Transparent Bridging ? [7:7126]
Hi Group, I vill say ziss only vonce. Okay, its my second attempt at trying to work out how I can bridge IP across to 2500's. I have 2 2500's configured with "no ip routing". 2 PC's are connected at either end, i.e one to bridge 1 and one to bridge 2. I have a sniffer on both PC's. I am attempting to ping from one PC to the other. IEEE spanning tree is applied on both bridges. The bridges are connected via a serial cable and the serial ports of the bridges as well as the Ethernet ports are in bridge group 1. I have verified spanning tree operation and one of the serial ports has been elected root port on bridge 1, the other bridge is the designated bridge. Ref : Radia Perlman, Interconnections p.83. So far so good. I have configured the PC's with a default gateway to the IP address of each of the bridges. When I attempt to ping from one PC to the other, I can see from my Sniffer trace that the PC ARP's for the MAC Address of the bridge, this ARP is successful and the PC then sends out an ICMP echo request. This echo request appears to be my problem since the destination MAC address of this packet contains the Ethernet Mac address of the local bridge and the local bridge consequently disregards the packet. Should the PC have an ARP entry installed for the destination IP address that I am pinging ? Has anyone achieved this scenario ? or am I way off mark with my thinking here. The reason I set this LAB up was because so many questions appear to be being asked at CCIE written level akin to this setup i.e can PC 1 ping PC 2 in similar arrangement using (RSRB/DLSW+/SRB etc) Any comments welcome. Regards, Phil. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=7126&t=7126 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Transparent Bridging ? [7:7126]
The PC shouldn't ARP for a bridge. A bridge is transparent. It should ARP for the end station. Something is weird with addressing and submasks. Priscilla At 03:22 PM 6/4/01, Philip Barker wrote: >Hi Group, > I vill say ziss only vonce. > >Okay, its my second attempt at trying to work out how I can bridge IP across >to 2500's. > >I have 2 2500's configured with "no ip routing". 2 PC's are connected at >either end, i.e one to bridge 1 >and one to bridge 2. I have a sniffer on both PC's. I am attempting to ping >from one PC to the other. >IEEE spanning tree is applied on both bridges. The bridges are connected via >a >serial cable and the serial >ports of the bridges as well as the Ethernet ports are in bridge group 1. > >I have verified spanning tree operation and one of the serial ports has been >elected root port on bridge 1, >the other bridge is the designated bridge. Ref : Radia Perlman, >Interconnections p.83. >So far so good. > >I have configured the PC's with a default gateway to the IP address of each >of >the bridges. >When I attempt to ping from one PC to the other, I can see from my Sniffer >trace that the PC ARP's for >the MAC Address of the bridge, this ARP is successful and the PC then sends >out an ICMP echo request. >This echo request appears to be my problem since the destination MAC address >of this packet contains >the Ethernet Mac address of the local bridge and the local bridge >consequently >disregards the packet. >Should the PC have an ARP entry installed for the destination IP address that >I am pinging ? > >Has anyone achieved this scenario ? or am I way off mark with my thinking >here. > >The reason I set this LAB up was because so many questions appear to be being >asked at CCIE written level >akin to this setup i.e can PC 1 ping PC 2 in similar arrangement using >(RSRB/DLSW+/SRB etc) > >Any comments welcome. > >Regards, > >Phil. Priscilla Oppenheimer http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=7130&t=7126 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Transparent Bridging ? [7:7126]
It sounds to me like you still have a layer three address somehwere on one of your routers, and that you maight still have a default gateway on one of your PCs pointing to that adx. I would pose the question, are both PC's configured to be on the same network? DO they have the same mask? If either of them have a default gateway configured I would turn that off for the testing just to limit the number of variables. If the routers arte configured to be bridges they should be totally transparent. You should not be able to ARP them because ARP requires a destination IP address, and if they are just bridges they won't have any IP addresses my $.02 At 03:22 PM 06/04/2001 -0400, Philip Barker wrote: >Hi Group, >I vill say ziss only vonce. > >Okay, its my second attempt at trying to work out how I can bridge IP across >to 2500's. > >I have 2 2500's configured with "no ip routing". 2 PC's are connected at >either end, i.e one to bridge 1 >and one to bridge 2. I have a sniffer on both PC's. I am attempting to ping >from one PC to the other. >IEEE spanning tree is applied on both bridges. The bridges are connected via >a >serial cable and the serial >ports of the bridges as well as the Ethernet ports are in bridge group 1. > >I have verified spanning tree operation and one of the serial ports has been >elected root port on bridge 1, >the other bridge is the designated bridge. Ref : Radia Perlman, >Interconnections p.83. >So far so good. > >I have configured the PC's with a default gateway to the IP address of each >of >the bridges. >When I attempt to ping from one PC to the other, I can see from my Sniffer >trace that the PC ARP's for >the MAC Address of the bridge, this ARP is successful and the PC then sends >out an ICMP echo request. >This echo request appears to be my problem since the destination MAC address >of this packet contains >the Ethernet Mac address of the local bridge and the local bridge >consequently >disregards the packet. >Should the PC have an ARP entry installed for the destination IP address that >I am pinging ? > >Has anyone achieved this scenario ? or am I way off mark with my thinking >here. > >The reason I set this LAB up was because so many questions appear to be being >asked at CCIE written level >akin to this setup i.e can PC 1 ping PC 2 in similar arrangement using >(RSRB/DLSW+/SRB etc) > >Any comments welcome. > >Regards, > >Phil. Tom Pruneau Trainer Network Operations GENUITY 3 Van de Graff Drive Burlington Ma. 01803 24 Hr. Network Operations Center 800-436-8489 If you need to get a hold of me my hours are 8AM-4PM ET Mon-Fri --- This email is composed of 82% post consumer recycled data bits --- "Once in a while you get shown the light in the strangest of places if you look at it right" Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=7143&t=7126 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Transparent Bridging ? [7:7126]
Jeepers, Its working, though I'm not convinced as to why !!! Maybe it was when I swore at the bridges and told them Priscilla was on the case that they just through the towel in ??? Regards, Phil. PS : I'm gonna strip it down now working backwards until I break it again. - Original Message - From: "Priscilla Oppenheimer" To: "Philip Barker" ; Sent: Monday, June 04, 2001 8:27 PM Subject: Re: Transparent Bridging ? [7:7126] > The PC shouldn't ARP for a bridge. A bridge is transparent. It should ARP > for the end station. Something is weird with addressing and submasks. > > Priscilla > > At 03:22 PM 6/4/01, Philip Barker wrote: > >Hi Group, > > I vill say ziss only vonce. > > > >Okay, its my second attempt at trying to work out how I can bridge IP across > >to 2500's. > > > >I have 2 2500's configured with "no ip routing". 2 PC's are connected at > >either end, i.e one to bridge 1 > >and one to bridge 2. I have a sniffer on both PC's. I am attempting to ping > >from one PC to the other. > >IEEE spanning tree is applied on both bridges. The bridges are connected via > >a > >serial cable and the serial > >ports of the bridges as well as the Ethernet ports are in bridge group 1. > > > >I have verified spanning tree operation and one of the serial ports has been > >elected root port on bridge 1, > >the other bridge is the designated bridge. Ref : Radia Perlman, > >Interconnections p.83. > >So far so good. > > > >I have configured the PC's with a default gateway to the IP address of each > >of > >the bridges. > >When I attempt to ping from one PC to the other, I can see from my Sniffer > >trace that the PC ARP's for > >the MAC Address of the bridge, this ARP is successful and the PC then sends > >out an ICMP echo request. > >This echo request appears to be my problem since the destination MAC address > >of this packet contains > >the Ethernet Mac address of the local bridge and the local bridge > >consequently > >disregards the packet. > >Should the PC have an ARP entry installed for the destination IP address that > >I am pinging ? > > > >Has anyone achieved this scenario ? or am I way off mark with my thinking > >here. > > > >The reason I set this LAB up was because so many questions appear to be being > >asked at CCIE written level > >akin to this setup i.e can PC 1 ping PC 2 in similar arrangement using > >(RSRB/DLSW+/SRB etc) > > > >Any comments welcome. > > > >Regards, > > > >Phil. > > > Priscilla Oppenheimer > http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=7146&t=7126 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Transparent Bridging ? [7:7126]
Check your addressing. Both PCs should be on the same subnet, and do not require a default gateway. A PC should not be configured with the IP address of a bridge as the default gateway. CM -Original Message- From: Philip Barker To: [EMAIL PROTECTED] Sent: 04/06/01 20:22 Subject: Transparent Bridging ? [7:7126] Hi Group, I vill say ziss only vonce. Okay, its my second attempt at trying to work out how I can bridge IP across to 2500's. I have 2 2500's configured with "no ip routing". 2 PC's are connected at either end, i.e one to bridge 1 and one to bridge 2. I have a sniffer on both PC's. I am attempting to ping from one PC to the other. IEEE spanning tree is applied on both bridges. The bridges are connected via a serial cable and the serial ports of the bridges as well as the Ethernet ports are in bridge group 1. I have verified spanning tree operation and one of the serial ports has been elected root port on bridge 1, the other bridge is the designated bridge. Ref : Radia Perlman, Interconnections p.83. So far so good. I have configured the PC's with a default gateway to the IP address of each of the bridges. When I attempt to ping from one PC to the other, I can see from my Sniffer trace that the PC ARP's for the MAC Address of the bridge, this ARP is successful and the PC then sends out an ICMP echo request. This echo request appears to be my problem since the destination MAC address of this packet contains the Ethernet Mac address of the local bridge and the local bridge consequently disregards the packet. Should the PC have an ARP entry installed for the destination IP address that I am pinging ? Has anyone achieved this scenario ? or am I way off mark with my thinking here. The reason I set this LAB up was because so many questions appear to be being asked at CCIE written level akin to this setup i.e can PC 1 ping PC 2 in similar arrangement using (RSRB/DLSW+/SRB etc) Any comments welcome. Regards, Phil. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=7147&t=7126 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Transparent Bridging ? [7:7126]
Indeed. Bridging using two 2500s as mentioned makes the routers operate strictly at layer 2. They will not forward packets of any kind using layer 3 methodology. In effect, they will not use any layer 3 forwarding mechanism so you cannot point a PC's def. gtwy to their local interface. Your PC will operate just fine without any gateway if all you need to do is establish connectivity to the other PC across the bridge. Both PCs should be in the same network of course. If they aren't then you know that you need to route and not bridge. Vijay Ramcharan -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of Charles Manafa Sent: Monday, June 04, 2001 4:17 PM To: [EMAIL PROTECTED] Subject: RE: Transparent Bridging ? [7:7126] Check your addressing. Both PCs should be on the same subnet, and do not require a default gateway. A PC should not be configured with the IP address of a bridge as the default gateway. CM -Original Message- From: Philip Barker To: [EMAIL PROTECTED] Sent: 04/06/01 20:22 Subject: Transparent Bridging ? [7:7126] Hi Group, I vill say ziss only vonce. Okay, its my second attempt at trying to work out how I can bridge IP across to 2500's. I have 2 2500's configured with "no ip routing". 2 PC's are connected at either end, i.e one to bridge 1 and one to bridge 2. I have a sniffer on both PC's. I am attempting to ping from one PC to the other. IEEE spanning tree is applied on both bridges. The bridges are connected via a serial cable and the serial ports of the bridges as well as the Ethernet ports are in bridge group 1. I have verified spanning tree operation and one of the serial ports has been elected root port on bridge 1, the other bridge is the designated bridge. Ref : Radia Perlman, Interconnections p.83. So far so good. I have configured the PC's with a default gateway to the IP address of each of the bridges. When I attempt to ping from one PC to the other, I can see from my Sniffer trace that the PC ARP's for the MAC Address of the bridge, this ARP is successful and the PC then sends out an ICMP echo request. This echo request appears to be my problem since the destination MAC address of this packet contains the Ethernet Mac address of the local bridge and the local bridge consequently disregards the packet. Should the PC have an ARP entry installed for the destination IP address that I am pinging ? Has anyone achieved this scenario ? or am I way off mark with my thinking here. The reason I set this LAB up was because so many questions appear to be being asked at CCIE written level akin to this setup i.e can PC 1 ping PC 2 in similar arrangement using (RSRB/DLSW+/SRB etc) Any comments welcome. Regards, Phil. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=7151&t=7126 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Transparent Bridging ? [7:7126]
OK, more than you ever wanted to know... The setup of the PCs is really no different than if they are on the same hub, switch vlan, or directly connected via a twist cable. The configuration of the PCs has to be done in one of two ways: 1. Set the PCs to the same ip subnet and mask (the default gateway doesn't matter, it won't be used). 2. Set the PCs to entirely different ip subnets (or the same, as long as the ip address is not identical or a broadcast address) and set the default gateway the same as the ip address. First Option: - Set the PCs to the same ip subnet and mask (the default gateway doesn't matter, it won't be used). For example: PC#1: IP: 10.100.1.20 MASK: 255.255.255.0 GW: 0.0.0.0 (or blank, depending on OS) PC#2: IP: 10.100.1.21 MASK: 255.255.255.0 GW: 0.0.0.0 The reason the default gateway doesn't matter is because both PC's are on the same IP subnet. The default gateway is only used if you try to communicate (ping) an ip subnet that is not local to the PC. On PC#1, ping your loopback (ping localhost on Windows), then ping your interface (ping 10.100.1.20) see above, then ping the other PC (ping 10.100.1.21). The reason for pinging your loopback and your own interface is to verify that your IP stack is functioning and configured properly before you blame the 'network'. Since the two PCs don't actually use the IP addresses to communicate, you can see what is actually going on by typing 'arp -a' in Windows to see the local ARP cache. You should see the IP address of PC#2 (10.100.1.21) and the MAC address. When you typed 'ping 10.100.1.21' on PC#1 (above), PC#1 actually: a. Sent an ARP request on the wire (you will see this on your sniffer) looking for the MAC address that answers to IP address 10.100.1.21. b. Provided only one machine on this segment (hub, switch vlan, etc.) is configured with this IP address, PC#2 will be the only PC to answer that ARP request. c. PC#1 will populate its local ARP cache with the IP address to MAC address mapping d. All communication with PC#2 will be with the MAC Address of PC#2 (not the IP Address). The reason for the IP address is to make it easier for humans to manage device addressing, the computers use only layer 1 (the cabling, hub) and layer 2 (mac address, bridge) to send information to each other. This is why you cannot ping an IP address on a different subnet (192.168.255.1 for example). The PC will try to use a default gateway to get there, which isn't configured and doesn't exist. To illustrate this point a little better, let me explain the second option for configuring the PCs: Second Option: -- Set the PCs to entirely different ip subnets (or the same, as long as the ip address is not identical or a broadcast address) and set the default gateway the same as the ip address. For example: PC#1: IP: 192.168.255.26 MASK: 255.255.255.0 GW: 192.168.255.26 PC#2: IP: 10.1.50.201 MASK: 255.0.0.0 GW: 10.1.50.201 Notice that the IP address and default gateway are identical on each individual PC. Now, why would you ever do this? To illustrate a point. If you would ping PC#2 (10.1.50.201) from PC#1 (192.168.255.26), it will work!!! (Assuming you started by verifying that you could ping localhost and your own interface). Why does this work? Because, by setting the ip address and default gateway the same, you tell the PC to ARP for everything. Even though the two PCs are configured on different IP subnets, the PCs don't care because they really use their MAC addresses to communicate. So, PC#1 sends and arp request for 10.1.50.201 on the wire and PC#2 responds, PC#1 adds the MAC address to its ARP cache and will send all further IP packets destined for 10.1.50.201 to the MAC address of PC#2. Does this clear anything up? Here are sample configs for your two routers: R1 -- ! the following line is NOT necessary if you don't put ip addresses ! on the individual interfaces, like this config ! no ip routing ! interface ethernet0 no ip address bridge-group 1 no shut ! interface serial0 desc DCE no ip address clockrate 56000 bridge-group 1 no shut ! bridge 1 protocol ieee ! end R2 -- ! the following line is NOT necessary if you don't put ip addresses ! on the individual interfaces, like this config ! no ip routing ! interface ethernet0 no ip address bridge-group 1 no shut ! interface serial0 desc DTE no ip address bridge-group 1 no shut ! bridge 1 protocol ieee ! end Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=7181&t=7126 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Transparent Bridging ? [7:7126]
Thanks for the excellent answer Rick. I now have it hammered down. PS : for all those who spotted my Gaff, I was on different networks at either end. Blush. Regards, Phil. - Original Message - From: "Rick Seiler" To: Sent: Tuesday, June 05, 2001 1:04 AM Subject: RE: Transparent Bridging ? [7:7126] > OK, more than you ever wanted to know... > > The setup of the PCs is really no different than if they are on the same > hub, switch vlan, or directly connected via a twist cable. The configuration > of the PCs has to be done in one of two ways: > > 1. Set the PCs to the same ip subnet and mask (the default gateway doesn't > matter, it won't be used). > > 2. Set the PCs to entirely different ip subnets (or the same, as long as the > ip address is not identical or a broadcast address) and set the default > gateway the same as the ip address. > > First Option: > - > > Set the PCs to the same ip subnet and mask (the default gateway doesn't > matter, it won't be used). > > For example: > > PC#1: > IP: 10.100.1.20 > MASK: 255.255.255.0 > GW: 0.0.0.0 (or blank, depending on OS) > > PC#2: > IP: 10.100.1.21 > MASK: 255.255.255.0 > GW: 0.0.0.0 > > The reason the default gateway doesn't matter is because both PC's are on > the same IP subnet. The default gateway is only used if you try to > communicate (ping) an ip subnet that is not local to the PC. > > On PC#1, ping your loopback (ping localhost on Windows), > then ping your interface (ping 10.100.1.20) see above, > then ping the other PC (ping 10.100.1.21). > > The reason for pinging your loopback and your own interface is to verify > that your IP stack is functioning and configured properly before you blame > the 'network'. > > Since the two PCs don't actually use the IP addresses to communicate, you > can see what is actually going on by typing 'arp -a' in Windows to see the > local ARP cache. You should see the IP address of PC#2 (10.100.1.21) and > the MAC address. When you typed 'ping 10.100.1.21' on PC#1 (above), PC#1 > actually: > > a. Sent an ARP request on the wire (you will see this on your sniffer) > looking for the MAC address that answers to IP address 10.100.1.21. > > b. Provided only one machine on this segment (hub, switch vlan, etc.) is > configured with this IP address, PC#2 will be the only PC to answer that ARP > request. > > c. PC#1 will populate its local ARP cache with the IP address to MAC address > mapping > > d. All communication with PC#2 will be with the MAC Address of PC#2 (not the > IP Address). The reason for the IP address is to make it easier for humans > to manage device addressing, the computers use only layer 1 (the cabling, > hub) and layer 2 (mac address, bridge) to send information to each other. > > This is why you cannot ping an IP address on a different subnet > (192.168.255.1 for example). The PC will try to use a default gateway to > get there, which isn't configured and doesn't exist. > > > To illustrate this point a little better, let me explain the second option > for configuring the PCs: > > Second Option: > -- > > Set the PCs to entirely different ip subnets (or the same, as long as the ip > address is not identical or a broadcast address) and set the default gateway > the same as the ip address. > > For example: > > PC#1: > IP: 192.168.255.26 > MASK: 255.255.255.0 > GW: 192.168.255.26 > > PC#2: > IP: 10.1.50.201 > MASK: 255.0.0.0 > GW: 10.1.50.201 > > Notice that the IP address and default gateway are identical on each > individual PC. > > Now, why would you ever do this? To illustrate a point. If you would ping > PC#2 (10.1.50.201) from PC#1 (192.168.255.26), it will work!!! (Assuming you > started by verifying that you could ping localhost and your own interface). > > Why does this work? Because, by setting the ip address and default gateway > the same, you tell the PC to ARP for everything. Even though the two PCs > are configured on different IP subnets, the PCs don't care because they > really use their MAC addresses to communicate. So, PC#1 sends and arp > request for 10.1.50.201 on the wire and PC#2 responds, PC#1 adds the MAC > address to its ARP cache and will send all further IP packets destined for > 10.1.50.201 to the MAC address of PC#2. > > > Does this clear anything up? Here are sample configs for your two routers: > > R1 > -- > > ! the following line is NOT necessary if you don't put ip addresses > ! on the individual interfaces, like this config > ! > no ip routing > ! > interface ethernet0 > no ip address
