RE: Amazing Spanning Tree [7:74594]
Also remember that the blocked port isn't in a down state because it still needs to listen to BPDUs to know when a topology change occurs. If it didn't, it wouldn't know when it needs to transition to forward state, if necessary. Just my 0.02... Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=74930t=74594 -- **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Re: Amazing Spanning Tree [7:74594]
dear friend, what u r seeing is absolutly normal you will never see both ends of the link will never go blocking. The way spanning tree works is one end will be blocking and other forwarding. Remember the purpose of the STP is to have a single path to Root bridge. Blocking on one side o the link serves the purpose. Sandeep --- Curious wrote: Hello friends, I have an spanning tree question for you! I have a lot of switches connected between them, but I have seen something that I can not explain very well. Two of these switches are connected using two cables: Switch1 Switch2 Port 29 - Port 29 Port 30 - Port 30 I expected to see one port in blocking state (spanning-tree) and the other in forwarding state, but suprisingly I have seen that port 30 is in blocking state in Switch1 but it is in forwarding state in Switch 2. Let's see these outputs: Switch1#sh spanning-tree interface FastEthernet 0/29 Interface Fa0/29 (port 35) in Spanning tree 1 is FORWARDING Port path cost 19, Port priority 128 Designated root has priority 32768, address 0002.fd3c.18b5 Designated bridge has priority 32768, address 0005.5e0c.57b6 Designated port is 35, path cost 23 Timers: message age 0, forward delay 0, hold 0 Switch1#sh spanning-tree interface FastEthernet 0/30 Interface Fa0/30 (port 36) in Spanning tree 1 is FORWARDING Port path cost 19, Port priority 128 Designated root has priority 32768, address 0002.fd3c.18b5 Designated bridge has priority 32768, address 0005.5e0c.57b6 Designated port is 36, path cost 23 Timers: message age 0, forward delay 0, hold 0 BPDU: sent 264503, received 2 Switch2#sh spanning-tree interface FAstEthernet 0/29 Interface Fa0/29 (port 35) in Spanning tree 1 is FORWARDING Port path cost 19, Port priority 128 Designated root has priority 32768, address 0002.fd3c.18b5 Designated bridge has priority 32768, address 0005.5e0c.57b6 Designated port is 35, path cost 23 Timers: message age 4, forward delay 0, hold 0 BPDU: sent 2, received 264561 Switch2#sh spanning-tree interface FAstEthernet 0/30 Interface Fa0/30 (port 36) in Spanning tree 1 is BLOCKING Port path cost 19, Port priority 128 Designated root has priority 32768, address 0002.fd3c.18b5 Designated bridge has priority 32768, address 0005.5e0c.57b6 Designated port is 36, path cost 23 Timers: message age 3, forward delay 0, hold 0 BPDU: sent 2, received 264573 Why a port is in blocking state and the other is in forwarding??? I expected to see both ports in blocking, but one forwarding and the other blocking doesn't make sense!!! Thanks a lot! **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html __ Do you Yahoo!? Yahoo! SiteBuilder - Free, easy-to-use web site design software http://sitebuilder.yahoo.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=74629t=74594 -- **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
RE: Amazing Spanning Tree [7:74594]
The subject should be renamed Amazing Answers... Whether a port is blocking or not, or even if Spanning Tree is running on the device, has absolutely no bearing on whether the port is physically up or down. The rest of the info is acceptable, but to throw that little nugget of information in the reply skews the whole thing. Fred Reimer - CCNA Eclipsys Corporation, 200 Ashford Center North, Atlanta, GA 30338 Phone: 404-847-5177 Cell: 770-490-3071 Pager: 888-260-2050 NOTICE; This email contains confidential or proprietary information which may be legally privileged. It is intended only for the named recipient(s). If an addressing or transmission error has misdirected the email, please notify the author by replying to this message. If you are not the named recipient, you are not authorized to use, disclose, distribute, copy, print or rely on this email, and should immediately delete it from your computer. -Original Message- From: Larry Letterman [mailto:[EMAIL PROTECTED] Sent: Monday, September 01, 2003 2:50 PM To: [EMAIL PROTECTED] Subject: RE: Amazing Spanning Tree [7:74594] The root switch will always be in forwarding. The downstream switch will Always be in blocking mode ...thats why the link is up/up... Larry Letterman Cisco Systems -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Sent: Monday, September 01, 2003 8:21 AM To: [EMAIL PROTECTED] Subject: Re: Amazing Spanning Tree [7:74594] Hello Marko, you said: I might be giving you wrong answer, but if one port is in blocking and the other one in blocking state, link is down in any case. The whole point of STP is acomplished But this is not right, my ports are up/up, but one of them is in forwarding state and the other in blocking :) :) I expected to see both ports in blocking, not one in forwarding and the other in blocking! **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=74653t=74594 -- **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
RE: Amazing Spanning Tree [7:74594]
The problem with analogies is that they often help you understand the
correct answer to a question, but seldom help you understand the why
behind the answer. The analogies I like to use most often are the models of
the protocols themselves. Think of each protocol as a state machine, or
rather state machines running on each router/switch in the network, and you
will seldom get the answer wrong. If you understand how that state machine
works and run it in your head, then you really }can't{ get the wrong answer.
I'd point Curious here:
http://standards.ieee.org/getieee802/
and just tell him/her to read the IEEE specs. It's all clear as day. It's
unbelievable how many network engineers don't even keep a copy of the
standards (IEEE specs, RFCs) they are supposed to be implementing in their
toolkit, and even more amazing how many of them haven't even read the
standards at least once.
Fred Reimer - CCNA
Eclipsys Corporation, 200 Ashford Center North, Atlanta, GA 30338
Phone: 404-847-5177 Cell: 770-490-3071 Pager: 888-260-2050
NOTICE; This email contains confidential or proprietary information which
may be legally privileged. It is intended only for the named recipient(s).
If an addressing or transmission error has misdirected the email, please
notify the author by replying to this message. If you are not the named
recipient, you are not authorized to use, disclose, distribute, copy, print
or rely on this email, and should immediately delete it from your computer.
-Original Message-
From: Fred Richards [mailto:[EMAIL PROTECTED]
Sent: Monday, September 01, 2003 10:44 AM
To: [EMAIL PROTECTED]
Subject: Re: Amazing Spanning Tree [7:74594]
I always like to think of Spanning Tree in respect to the numbers on a
clock. If the information goes around in a circle, you only need 1
blocking port to disrupt the circle. You don't need to block in two
parts of the circle. The Sybex CCNA book had an excellent example of
this (I got my CCNA June 30th, 911/1000)... they had the explaination on
one page, then you turn the page and they had 5 switches. The diagram
made all the sense in the world. Which is kind of where I got my clock
analogy. If you're disrupting the loop at the 12 spot on the clock,
you don't need to disrupt it anywhere else.
-- Fred
Curious wrote:
Hello friends, I have an spanning tree question for you!
I have a lot of switches connected between them, but I have seen
something that I can not explain very well. Two of these switches are
connected using two cables:
Switch1 Switch2
Port 29 - Port 29
Port 30 - Port 30
I expected to see one port in blocking state (spanning-tree) and the other
in forwarding state, but suprisingly I have seen that port 30 is in
blocking
state
in Switch1 but it is in forwarding state in Switch 2. Let's see these
outputs:
Switch1#sh spanning-tree interface FastEthernet 0/29
Interface Fa0/29 (port 35) in Spanning tree 1 is FORWARDING
Port path cost 19, Port priority 128
Designated root has priority 32768, address 0002.fd3c.18b5
Designated bridge has priority 32768, address 0005.5e0c.57b6
Designated port is 35, path cost 23
Timers: message age 0, forward delay 0, hold 0
Switch1#sh spanning-tree interface FastEthernet 0/30
Interface Fa0/30 (port 36) in Spanning tree 1 is FORWARDING
Port path cost 19, Port priority 128
Designated root has priority 32768, address 0002.fd3c.18b5
Designated bridge has priority 32768, address 0005.5e0c.57b6
Designated port is 36, path cost 23
Timers: message age 0, forward delay 0, hold 0
BPDU: sent 264503, received 2
Switch2#sh spanning-tree interface FAstEthernet 0/29
Interface Fa0/29 (port 35) in Spanning tree 1 is FORWARDING
Port path cost 19, Port priority 128
Designated root has priority 32768, address 0002.fd3c.18b5
Designated bridge has priority 32768, address 0005.5e0c.57b6
Designated port is 35, path cost 23
Timers: message age 4, forward delay 0, hold 0
BPDU: sent 2, received 264561
Switch2#sh spanning-tree interface FAstEthernet 0/30
Interface Fa0/30 (port 36) in Spanning tree 1 is BLOCKING
Port path cost 19, Port priority 128
Designated root has priority 32768, address 0002.fd3c.18b5
Designated bridge has priority 32768, address 0005.5e0c.57b6
Designated port is 36, path cost 23
Timers: message age 3, forward delay 0, hold 0
BPDU: sent 2, received 264573
Why a port is in blocking state and the other is in forwarding??? I
expected to
see both ports in blocking, but one forwarding and the other blocking
doesn't make
sense!!!
Thanks a lot!
**Please support GroupStudy by purchasing from the GroupStudy Store:
http://shop.groupstudy.com
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RE: Amazing Spanning Tree [7:74594]
Hello friends, I want to thank every answer to this post. I knew that a port with spanning tree in blockin state has not any relation with being down, I was surprised with some answers. What surprised me, is that one port were in forwarding state and the port in front be in blocking state. For me, there is no sense in having one port in forwarding state when the port in front is in blocking state, why not both in blocking state?? I know that RFC's stablish the rules but I want to understand the sense. Thanks again!! Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=74666t=74594 -- **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
RE: Amazing Spanning Tree [7:74594]
Think of it like this. Each switch is supposed to block redundant ports leading to the root bridge. Say Switch1 and Switch2 are interlinked, and also have downlink connections to the root bridge, like this: Switch1 -- Switch2 | | | | Core1 -- Core2 Say Core1 is the root bridge. Assuming equal cost links (All Gigabit ports) and no tweaking, what link would be blocked? It should be the inter-link port between Switch1 and Switch2 on Switch1's side. Now, this is not exactly how it works, but if it helps you can think of it like, since Switch1 blocked its port going to Switch2, Switch2 can't See the root bridge on that port, so it keeps it open. Like I said, that's not exactly how it works, but if it helps you understand what port gets blocked then so be it. I'd suggest reading the IEEE docs though. They are a little hard to follow, because of the similar terms it uses (too many Designated for my taste), but it is the definitive text on the topic. Fred Reimer - CCNA Eclipsys Corporation, 200 Ashford Center North, Atlanta, GA 30338 Phone: 404-847-5177 Cell: 770-490-3071 Pager: 888-260-2050 NOTICE; This email contains confidential or proprietary information which may be legally privileged. It is intended only for the named recipient(s). If an addressing or transmission error has misdirected the email, please notify the author by replying to this message. If you are not the named recipient, you are not authorized to use, disclose, distribute, copy, print or rely on this email, and should immediately delete it from your computer. -Original Message- From: Curious [mailto:[EMAIL PROTECTED] Sent: Tuesday, September 02, 2003 12:02 PM To: [EMAIL PROTECTED] Subject: RE: Amazing Spanning Tree [7:74594] Hello friends, I want to thank every answer to this post. I knew that a port with spanning tree in blockin state has not any relation with being down, I was surprised with some answers. What surprised me, is that one port were in forwarding state and the port in front be in blocking state. For me, there is no sense in having one port in forwarding state when the port in front is in blocking state, why not both in blocking state?? I know that RFC's stablish the rules but I want to understand the sense. Thanks again!! **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=74674t=74594 -- **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
RE: Amazing Spanning Tree [7:74594]
There could be hosts inbetween (think hub). Thanks, Zsombor Curious wrote: Hello friends, I want to thank every answer to this post. I knew that a port with spanning tree in blockin state has not any relation with being down, I was surprised with some answers. What surprised me, is that one port were in forwarding state and the port in front be in blocking state. For me, there is no sense in having one port in forwarding state when the port in front is in blocking state, why not both in blocking state?? I know that RFC's stablish the rules but I want to understand the sense. Thanks again!! Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=74672t=74594 -- **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Re: Amazing Spanning Tree [7:74594]
Reimer, Fred wrote: Think of it like this. Each switch is supposed to block redundant ports leading to the root bridge. Say Switch1 and Switch2 are interlinked, and also have downlink connections to the root bridge, like this: Switch1 -- Switch2 | | | | Core1 -- Core2 Say Core1 is the root bridge. Assuming equal cost links (All Gigabit ports) and no tweaking, what link would be blocked? It should be the inter-link port between Switch1 and Switch2 on Switch1's side. Now, this is not exactly how it works, but if it helps you can think of it like, since Switch1 blocked its port going to Switch2, Switch2 can't See the root bridge on that port, so it keeps it open. Like I said, that's not exactly how it works, but if it helps you understand what port gets blocked then so be it. I'd suggest reading the IEEE docs though. They are a little hard to follow, because of the similar terms it uses (too many Designated for my taste), but it is the definitive text on the topic. Another more readable doc on spanning would be Radia Perlman's Interconnections. Dave Fred Reimer - CCNA Eclipsys Corporation, 200 Ashford Center North, Atlanta, GA 30338 Phone: 404-847-5177 Cell: 770-490-3071 Pager: 888-260-2050 NOTICE; This email contains confidential or proprietary information which may be legally privileged. It is intended only for the named recipient(s). If an addressing or transmission error has misdirected the email, please notify the author by replying to this message. If you are not the named recipient, you are not authorized to use, disclose, distribute, copy, print or rely on this email, and should immediately delete it from your computer. -Original Message- From: Curious [mailto:[EMAIL PROTECTED] Sent: Tuesday, September 02, 2003 12:02 PM To: [EMAIL PROTECTED] Subject: RE: Amazing Spanning Tree [7:74594] Hello friends, I want to thank every answer to this post. I knew that a port with spanning tree in blockin state has not any relation with being down, I was surprised with some answers. What surprised me, is that one port were in forwarding state and the port in front be in blocking state. For me, there is no sense in having one port in forwarding state when the port in front is in blocking state, why not both in blocking state?? I know that RFC's stablish the rules but I want to understand the sense. Thanks again!! **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html -- David Madland CCIE# 2016 Sr. Network Engineer Qwest Communications 612-664-3367 Emotion should reflect reason not guide it Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=74679t=74594 -- **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
RE: Amazing Spanning Tree [7:74594]
i think he has... forw. \ /blked /---\ switch1 switch2 \/ blked/ \forw. not that it makes any sense to me either. it would seem logical that one entire link would be blocked and one forwarding. -Original Message- From: Reimer, Fred [mailto:[EMAIL PROTECTED] Sent: Tuesday, September 02, 2003 10:48 AM To: [EMAIL PROTECTED] Subject: RE: Amazing Spanning Tree [7:74594] Think of it like this. Each switch is supposed to block redundant ports leading to the root bridge. Say Switch1 and Switch2 are interlinked, and also have downlink connections to the root bridge, like this: Switch1 -- Switch2 | | | | Core1 -- Core2 Say Core1 is the root bridge. Assuming equal cost links (All Gigabit ports) and no tweaking, what link would be blocked? It should be the inter-link port between Switch1 and Switch2 on Switch1's side. Now, this is not exactly how it works, but if it helps you can think of it like, since Switch1 blocked its port going to Switch2, Switch2 can't See the root bridge on that port, so it keeps it open. Like I said, that's not exactly how it works, but if it helps you understand what port gets blocked then so be it. I'd suggest reading the IEEE docs though. They are a little hard to follow, because of the similar terms it uses (too many Designated for my taste), but it is the definitive text on the topic. Fred Reimer - CCNA Eclipsys Corporation, 200 Ashford Center North, Atlanta, GA 30338 Phone: 404-847-5177 Cell: 770-490-3071 Pager: 888-260-2050 NOTICE; This email contains confidential or proprietary information which may be legally privileged. It is intended only for the named recipient(s). If an addressing or transmission error has misdirected the email, please notify the author by replying to this message. If you are not the named recipient, you are not authorized to use, disclose, distribute, copy, print or rely on this email, and should immediately delete it from your computer. -Original Message- From: Curious [mailto:[EMAIL PROTECTED] Sent: Tuesday, September 02, 2003 12:02 PM To: [EMAIL PROTECTED] Subject: RE: Amazing Spanning Tree [7:74594] Hello friends, I want to thank every answer to this post. I knew that a port with spanning tree in blockin state has not any relation with being down, I was surprised with some answers. What surprised me, is that one port were in forwarding state and the port in front be in blocking state. For me, there is no sense in having one port in forwarding state when the port in front is in blocking state, why not both in blocking state?? I know that RFC's stablish the rules but I want to understand the sense. Thanks again!! **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=74681t=74594 -- **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
RE: Amazing Spanning Tree [7:74594]
As Zsombor pointed out, the link in between the switches is a segment. It could contain hosts. Remember that Spanning Tree was created way before there was anything like a switch (which is just a fast multi-port bridge). Think of ThickNet Ethernet with DEC DELNIs and vampire clamps. If both switches blocked on that port then no hosts on that segment (granted there are none in this specific example, but there could be) would be able to communicate. Fred Reimer - CCNA Eclipsys Corporation, 200 Ashford Center North, Atlanta, GA 30338 Phone: 404-847-5177 Cell: 770-490-3071 Pager: 888-260-2050 NOTICE; This email contains confidential or proprietary information which may be legally privileged. It is intended only for the named recipient(s). If an addressing or transmission error has misdirected the email, please notify the author by replying to this message. If you are not the named recipient, you are not authorized to use, disclose, distribute, copy, print or rely on this email, and should immediately delete it from your computer. -Original Message- From: Wilmes, Rusty [mailto:[EMAIL PROTECTED] Sent: Tuesday, September 02, 2003 2:59 PM To: 'Reimer, Fred'; [EMAIL PROTECTED] Subject: RE: Amazing Spanning Tree [7:74594] i think he has... forw. \ /blked /---\ switch1 switch2 \/ blked/ \forw. not that it makes any sense to me either. it would seem logical that one entire link would be blocked and one forwarding. -Original Message- From: Reimer, Fred [mailto:[EMAIL PROTECTED] Sent: Tuesday, September 02, 2003 10:48 AM To: [EMAIL PROTECTED] Subject: RE: Amazing Spanning Tree [7:74594] Think of it like this. Each switch is supposed to block redundant ports leading to the root bridge. Say Switch1 and Switch2 are interlinked, and also have downlink connections to the root bridge, like this: Switch1 -- Switch2 | | | | Core1 -- Core2 Say Core1 is the root bridge. Assuming equal cost links (All Gigabit ports) and no tweaking, what link would be blocked? It should be the inter-link port between Switch1 and Switch2 on Switch1's side. Now, this is not exactly how it works, but if it helps you can think of it like, since Switch1 blocked its port going to Switch2, Switch2 can't See the root bridge on that port, so it keeps it open. Like I said, that's not exactly how it works, but if it helps you understand what port gets blocked then so be it. I'd suggest reading the IEEE docs though. They are a little hard to follow, because of the similar terms it uses (too many Designated for my taste), but it is the definitive text on the topic. Fred Reimer - CCNA Eclipsys Corporation, 200 Ashford Center North, Atlanta, GA 30338 Phone: 404-847-5177 Cell: 770-490-3071 Pager: 888-260-2050 NOTICE; This email contains confidential or proprietary information which may be legally privileged. It is intended only for the named recipient(s). If an addressing or transmission error has misdirected the email, please notify the author by replying to this message. If you are not the named recipient, you are not authorized to use, disclose, distribute, copy, print or rely on this email, and should immediately delete it from your computer. -Original Message- From: Curious [mailto:[EMAIL PROTECTED] Sent: Tuesday, September 02, 2003 12:02 PM To: [EMAIL PROTECTED] Subject: RE: Amazing Spanning Tree [7:74594] Hello friends, I want to thank every answer to this post. I knew that a port with spanning tree in blockin state has not any relation with being down, I was surprised with some answers. What surprised me, is that one port were in forwarding state and the port in front be in blocking state. For me, there is no sense in having one port in forwarding state when the port in front is in blocking state, why not both in blocking state?? I know that RFC's stablish the rules but I want to understand the sense. Thanks again!! **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=74683t=74594 -- **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
RE: Amazing Spanning Tree [7:74594]
Brave!! This is exactly the kind of answer I was waiting for. Just common sense, now I understand it, and I feel like a stupid because the answer is obvious. Thanks Zsombor Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=74685t=74594 -- **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
RE: Amazing Spanning Tree [7:74594]
I know this do not answer your question but did you saw the timers of Forwarding Delay in the Switches?? Regards Victor. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=74596t=74594 -- **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Re: Amazing Spanning Tree [7:74594]
I expected to see one port in blocking state (spanning-tree) and the other in forwarding state, but suprisingly I have seen that port 30 is in blocking state in Switch1 but it is in forwarding state in Switch 2. I might be giving you wrong answer, but if one port is in blocking and the other one in blocking state, link is down in any case. The whole point of STP is acomplished. If you recreate te connection scenario, I wouldn't be too surprised if the situation is the other way round (depending on the entire topology, of course). This might just mean that one switch finished STP faster than the other one. I think this behaviour is perfectly fine. Marko. P.S. As usual, if I'm horribly wrong, I'd like to be corrected. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=74597t=74594 -- **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Re: Amazing Spanning Tree [7:74594]
I might be giving you wrong answer, but if one port is in blocking and the other one in blocking state, link is down in any case. The whole point of STP is acomplished. Should be read as: I might be giving you wrong answer, but if one port is in blocking and the other one in forwarding state, link is down in any case. The whole point of STP is acomplished. ;-) Marko. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=74598t=74594 -- **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Re: Amazing Spanning Tree [7:74594]
I always like to think of Spanning Tree in respect to the numbers on a clock. If the information goes around in a circle, you only need 1 blocking port to disrupt the circle. You don't need to block in two parts of the circle. The Sybex CCNA book had an excellent example of this (I got my CCNA June 30th, 911/1000)... they had the explaination on one page, then you turn the page and they had 5 switches. The diagram made all the sense in the world. Which is kind of where I got my clock analogy. If you're disrupting the loop at the 12 spot on the clock, you don't need to disrupt it anywhere else. -- Fred Curious wrote: Hello friends, I have an spanning tree question for you! I have a lot of switches connected between them, but I have seen something that I can not explain very well. Two of these switches are connected using two cables: Switch1 Switch2 Port 29 - Port 29 Port 30 - Port 30 I expected to see one port in blocking state (spanning-tree) and the other in forwarding state, but suprisingly I have seen that port 30 is in blocking state in Switch1 but it is in forwarding state in Switch 2. Let's see these outputs: Switch1#sh spanning-tree interface FastEthernet 0/29 Interface Fa0/29 (port 35) in Spanning tree 1 is FORWARDING Port path cost 19, Port priority 128 Designated root has priority 32768, address 0002.fd3c.18b5 Designated bridge has priority 32768, address 0005.5e0c.57b6 Designated port is 35, path cost 23 Timers: message age 0, forward delay 0, hold 0 Switch1#sh spanning-tree interface FastEthernet 0/30 Interface Fa0/30 (port 36) in Spanning tree 1 is FORWARDING Port path cost 19, Port priority 128 Designated root has priority 32768, address 0002.fd3c.18b5 Designated bridge has priority 32768, address 0005.5e0c.57b6 Designated port is 36, path cost 23 Timers: message age 0, forward delay 0, hold 0 BPDU: sent 264503, received 2 Switch2#sh spanning-tree interface FAstEthernet 0/29 Interface Fa0/29 (port 35) in Spanning tree 1 is FORWARDING Port path cost 19, Port priority 128 Designated root has priority 32768, address 0002.fd3c.18b5 Designated bridge has priority 32768, address 0005.5e0c.57b6 Designated port is 35, path cost 23 Timers: message age 4, forward delay 0, hold 0 BPDU: sent 2, received 264561 Switch2#sh spanning-tree interface FAstEthernet 0/30 Interface Fa0/30 (port 36) in Spanning tree 1 is BLOCKING Port path cost 19, Port priority 128 Designated root has priority 32768, address 0002.fd3c.18b5 Designated bridge has priority 32768, address 0005.5e0c.57b6 Designated port is 36, path cost 23 Timers: message age 3, forward delay 0, hold 0 BPDU: sent 2, received 264573 Why a port is in blocking state and the other is in forwarding??? I expected to see both ports in blocking, but one forwarding and the other blocking doesn't make sense!!! Thanks a lot! **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=74602t=74594 -- **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Re: Amazing Spanning Tree [7:74594]
I always like to think of Spanning Tree in respect to the numbers on a clock. If the information goes around in a circle, you only need 1 blocking port to disrupt the circle. You don't need to block in two parts of the circle. The Sybex CCNA book had an excellent example of this (I got my CCNA June 30th, 911/1000)... they had the explaination on one page, then you turn the page and they had 5 switches. The diagram made all the sense in the world. Which is kind of where I got my clock analogy. If you're disrupting the loop at the 12 spot on the clock, you don't need to disrupt it anywhere else. -- Fred Curious wrote: Hello friends, I have an spanning tree question for you! I have a lot of switches connected between them, but I have seen something that I can not explain very well. Two of these switches are connected using two cables: Switch1 Switch2 Port 29 - Port 29 Port 30 - Port 30 I expected to see one port in blocking state (spanning-tree) and the other in forwarding state, but suprisingly I have seen that port 30 is in blocking state in Switch1 but it is in forwarding state in Switch 2. Let's see these outputs: Switch1#sh spanning-tree interface FastEthernet 0/29 Interface Fa0/29 (port 35) in Spanning tree 1 is FORWARDING Port path cost 19, Port priority 128 Designated root has priority 32768, address 0002.fd3c.18b5 Designated bridge has priority 32768, address 0005.5e0c.57b6 Designated port is 35, path cost 23 Timers: message age 0, forward delay 0, hold 0 Switch1#sh spanning-tree interface FastEthernet 0/30 Interface Fa0/30 (port 36) in Spanning tree 1 is FORWARDING Port path cost 19, Port priority 128 Designated root has priority 32768, address 0002.fd3c.18b5 Designated bridge has priority 32768, address 0005.5e0c.57b6 Designated port is 36, path cost 23 Timers: message age 0, forward delay 0, hold 0 BPDU: sent 264503, received 2 Switch2#sh spanning-tree interface FAstEthernet 0/29 Interface Fa0/29 (port 35) in Spanning tree 1 is FORWARDING Port path cost 19, Port priority 128 Designated root has priority 32768, address 0002.fd3c.18b5 Designated bridge has priority 32768, address 0005.5e0c.57b6 Designated port is 35, path cost 23 Timers: message age 4, forward delay 0, hold 0 BPDU: sent 2, received 264561 Switch2#sh spanning-tree interface FAstEthernet 0/30 Interface Fa0/30 (port 36) in Spanning tree 1 is BLOCKING Port path cost 19, Port priority 128 Designated root has priority 32768, address 0002.fd3c.18b5 Designated bridge has priority 32768, address 0005.5e0c.57b6 Designated port is 36, path cost 23 Timers: message age 3, forward delay 0, hold 0 BPDU: sent 2, received 264573 Why a port is in blocking state and the other is in forwarding??? I expected to see both ports in blocking, but one forwarding and the other blocking doesn't make sense!!! Thanks a lot! **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=74601t=74594 -- **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Re: Amazing Spanning Tree [7:74594]
Hello Marko, you said: I might be giving you wrong answer, but if one port is in blocking and the other one in blocking state, link is down in any case. The whole point of STP is acomplished But this is not right, my ports are up/up, but one of them is in forwarding state and the other in blocking :) :) I expected to see both ports in blocking, not one in forwarding and the other in blocking! Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=74605t=74594 -- **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Re: Amazing Spanning Tree [7:74594]
Dear Friend Its the basics of STP Root Bridge - 29 30 - | | | | | | | X - 29 30 - 1) All the Ports in the root bridge will be in the forwarding state 2) When you have the parallel connection the first priority goes to the Path COST then to the Designated Cost then Port Priority 3) In your case all are same so they take the lowest port number internally to assign the forwarding state Hope this will help you Enjoy Regards Bani Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=74603t=74594 -- **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Re: Amazing Spanning Tree [7:74594]
Thanks bharani, I thought this, but neither Switch1 or Switch2 is the root bridge: Switch1:#sh spanning-tree Spanning tree 1 is executing the IEEE compatible Spanning Tree protocol Bridge Identifier has priority 32768, address 0005.5e0c.57b6 Configured hello time 2, max age 20, forward delay 15 Current root has priority 32768, address 0002.fd3c.18c1 Root port is 40, cost of root path is 23 Topology change flag not set, detected flag not set, changes 113816 Times: hold 1, topology change 35, notification 2 hello 2, max age 20, forward delay 15 Timers: hello 0, topology change 0, notification 0 Switch2: Switch2#sh spanning-tree Spanning tree 1 is executing the IEEE compatible Spanning Tree protocol Bridge Identifier has priority 32768, address 0005.5e0c.c5b5 Configured hello time 2, max age 20, forward delay 15 Current root has priority 32768, address 0002.fd3c.18b5 Root port is 35, cost of root path is 42 Topology change flag not set, detected flag not set, changes 113815 Times: hold 1, topology change 35, notification 2 hello 2, max age 20, forward delay 15 Timers: hello 0, topology change 0, notification 0 what do you think?? One of them could be the designated bridge, but it doesn't explain why one port is in forwarding and the port in front of it is in blockin. I think that our friend Fred is right. If you can break the ring in one point, why break it in two points?? Thanks. Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=74606t=74594 -- **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
RE: Amazing Spanning Tree [7:74594]
The root switch will always be in forwarding. The downstream switch will Always be in blocking mode ...thats why the link is up/up... Larry Letterman Cisco Systems -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Sent: Monday, September 01, 2003 8:21 AM To: [EMAIL PROTECTED] Subject: Re: Amazing Spanning Tree [7:74594] Hello Marko, you said: I might be giving you wrong answer, but if one port is in blocking and the other one in blocking state, link is down in any case. The whole point of STP is acomplished But this is not right, my ports are up/up, but one of them is in forwarding state and the other in blocking :) :) I expected to see both ports in blocking, not one in forwarding and the other in blocking! **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=74612t=74594 -- **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Re: Amazing Spanning Tree [7:74594]
That seems right to be. The link should not go down just because spanning tree is blocking a port. Curious wrote in message news:[EMAIL PROTECTED] Hello friends, I have an spanning tree question for you! I have a lot of switches connected between them, but I have seen something that I can not explain very well. Two of these switches are connected using two cables: Switch1 Switch2 Port 29 - Port 29 Port 30 - Port 30 I expected to see one port in blocking state (spanning-tree) and the other in forwarding state, but suprisingly I have seen that port 30 is in blocking state in Switch1 but it is in forwarding state in Switch 2. Let's see these outputs: Switch1#sh spanning-tree interface FastEthernet 0/29 Interface Fa0/29 (port 35) in Spanning tree 1 is FORWARDING Port path cost 19, Port priority 128 Designated root has priority 32768, address 0002.fd3c.18b5 Designated bridge has priority 32768, address 0005.5e0c.57b6 Designated port is 35, path cost 23 Timers: message age 0, forward delay 0, hold 0 Switch1#sh spanning-tree interface FastEthernet 0/30 Interface Fa0/30 (port 36) in Spanning tree 1 is FORWARDING Port path cost 19, Port priority 128 Designated root has priority 32768, address 0002.fd3c.18b5 Designated bridge has priority 32768, address 0005.5e0c.57b6 Designated port is 36, path cost 23 Timers: message age 0, forward delay 0, hold 0 BPDU: sent 264503, received 2 Switch2#sh spanning-tree interface FAstEthernet 0/29 Interface Fa0/29 (port 35) in Spanning tree 1 is FORWARDING Port path cost 19, Port priority 128 Designated root has priority 32768, address 0002.fd3c.18b5 Designated bridge has priority 32768, address 0005.5e0c.57b6 Designated port is 35, path cost 23 Timers: message age 4, forward delay 0, hold 0 BPDU: sent 2, received 264561 Switch2#sh spanning-tree interface FAstEthernet 0/30 Interface Fa0/30 (port 36) in Spanning tree 1 is BLOCKING Port path cost 19, Port priority 128 Designated root has priority 32768, address 0002.fd3c.18b5 Designated bridge has priority 32768, address 0005.5e0c.57b6 Designated port is 36, path cost 23 Timers: message age 3, forward delay 0, hold 0 BPDU: sent 2, received 264573 Why a port is in blocking state and the other is in forwarding??? I expected to see both ports in blocking, but one forwarding and the other blocking doesn't make sense!!! Thanks a lot! **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=74618t=74594 -- **Please support GroupStudy by purchasing from the GroupStudy Store: http://shop.groupstudy.com FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
