Well I can't see your configs but likely what is happening is that Cat4 and Cat1 are acting in a layer 2 capacity only on this path.
More accurately might be to think about it as R2-R5-VLAN567-Cat3-Cat3 loopback (don't forget to count those loopbacks as a hop) R2-R6-VLAN567-Cat3-Cat3 loopback R2-R4-VLAN??-Cat3-Cat3 loopback It would probably be a good idea for you to step through each path and view the costs and hops. Then try manipulating some of the costs. This is a topic you need to understand entirely. On Tue, Jul 12, 2011 at 5:19 PM, Alef <[email protected]> wrote: > Hey Marc, > To emphasise, this is for the 33.33.33.33 loopback, or Cat3 loopback route. > > I see: > R2-R5-Cat3 > R2-R6-Cat4-Cat3 > R2-R4-Cat1-Cat3 > > Why would i go through Cat2 ? So in my count it should prefer the route > through R5? > On Jul 12, 2011, at 11:05 PM, marc abel wrote: > >> You can see they all have an equal cost [110/66] of 66. Looking at >> your diagram I see >> >> R2-R4-Cat1-Cat2-Cat2 loopback >> R2-R5-Cat3-Cat2-Cat2 loopback >> R2-R6-Cat4-Cat2-Cat2 loopback >> >> Extra fiddling is one of the best ways to learn this stuff. >> >> On Tue, Jul 12, 2011 at 4:49 PM, Alef <[email protected]> wrote: >>> Thanks Marc. >>> >>> This was the problem: >>> R6#sh class-map type inspect >>> Class Map type inspect match-any corporate-to-private-class (id 1) >>> Match protocol telnet >>> Match protocol ssh >>> Match protocol ftp >>> >>> Once i added icmp all was well. I didn't actually expect the route to go >>> over that for some reason, nor do i understand why it had r6 in it's path >>> with equal distance, as there is at least one more l3 switch in between >>> compared to R5. Same for R4. Does it not see the "switches" as a hop or >>> something ? >>> O 33.33.33.33 [110/66] via 100.100.100.6, 00:13:27, Serial1/1.256 >>> [110/66] via 100.100.100.5, 00:13:27, Serial1/1.256 >>> [110/66] via 100.100.24.4, 00:07:08, Serial1/0.24 >>> >>> This is what i get for fiddling with labs designed for a different purpose >>> and then trying to add more functionality (or get more out of it) ;-) >>> >>> >>> On Jul 12, 2011, at 10:36 PM, marc abel wrote: >>> >>>> Layer 2 loops are caused because switches by default flood traffic out >>>> all ports, so any time you connect switches in a circular path a loop >>>> would form if not for spanning-tree. >>>> >>>> In layer 3 this is not the case. Since you have to specifically tell >>>> traffic where to route, making a circle does not make a loop. Routes >>>> make loops by referring back to a host that thinks its path is back to >>>> itself. So adding layer 3 interfaces is not the cause of the loops, >>>> incorrect routes are. >>>> >>>> Take this example >>>> >>>> R1. >>>> int g0/0 >>>> ip address 10.10.10.1 255.255.255.0 >>>> no shut >>>> ! >>>> ip route 6.6.6.6 255.255.255.255 10.10.10.2 >>>> >>>> R2. >>>> int g0/0 >>>> ip address 10.10.10.2 255.255.255.0 >>>> no shut >>>> ! >>>> ip route 6.6.6.6 255.255.255.255 10.10.10.1 >>>> >>>> >>>> Now try to traceroute to 6.6.6.6. R1 will send it to R2, R2 will send >>>> it to R1, R1 will send to R2, repeat until the TTL expires. This is a >>>> layer 3 loop. You will generally notice layer 3 loops by traffic not >>>> reaching its destination(and proved by traceroute), or by routes being >>>> repeatedly installed and removed from the routing table (debug ip >>>> routing). >>>> >>>> Layer 2 loops will generally either keep looping the traffic around so >>>> much that you lose access to the device and the whole damn network >>>> crashes, or if you are lucky you might not have it so bad and you will >>>> see a message in the logs that says something like host x.x.x.x is >>>> flapping between interface..... >>>> >>>> -Marc >>>> >>>> >>>> >>>> >>>> On Tue, Jul 12, 2011 at 3:37 PM, Alef <[email protected]> wrote: >>>>> No no redistribution. I tried to keep it as simple as possible. >>>>> Ok let me try my hand at some ascii art. >>>>> >>>>> But before i do that, is there some inherent stupid thing about putting >>>>> vlan interfaces in all the vlans on all the switches ( i have dot1q >>>>> trunks in x between all 4 switches). I can imagine in my network it would >>>>> create a loop. Just a hunch if i follow the paths. Would i not >>>>> automatically introduce L3 loops by doing that. I think ipexpert topology >>>>> is setup similar ? >>>>> >>>>> ok scratch that, i uploaded a small jpg >>>>> http://tinypic.com/r/fkqfqr/7 >>>>> >>>>> All switches loopbacks are reachable by at least 3 paths (2 trough the FR >>>>> cloud, and 1 other) >>>>> >>>>> R2# >>>>> O 11.11.11.11 [110/66] via 100.100.100.6, 01:01:51, Serial1/1.256 >>>>> [110/66] via 100.100.100.5, 01:01:51, Serial1/1.256 >>>>> [110/66] via 100.100.24.4, 00:00:43, Serial1/0.24 >>>>> 44.0.0.0/32 is subnetted, 1 subnets >>>>> O 44.44.44.44 [110/66] via 100.100.100.6, 01:01:51, Serial1/1.256 >>>>> [110/66] via 100.100.100.5, 01:01:51, Serial1/1.256 >>>>> [110/66] via 100.100.24.4, 00:00:43, Serial1/0.24 >>>>> >>>>> On a probably unrelated side note, anyone ever got : >>>>> %OSPF-4-ERRRCV: Received invalid packet: Bad Checksum from 100.100.14.1, >>>>> Vlan14 >>>>> >>>>> Cisco website says change the port or cable, which i did, and cable, well >>>>> considering it's a dynamips sim i did that as best as i could :-) >>>>> >>>>> Can't get the message to go away though. >>>>> >>>>> On Jul 12, 2011, at 5:24 PM, Di Bias, Steve wrote: >>>>> >>>>>> >>>>>> What makes you think you have any kind of loop? What are the symptoms? >>>>>> Are you redistributing anywhere? >>>>>> >>>>>> -----Original Message----- >>>>>> From: [email protected] >>>>>> [mailto:[email protected]] On Behalf Of Alef >>>>>> Sent: Tuesday, July 12, 2011 8:27 AM >>>>>> To: [email protected] IE >>>>>> Subject: [OSL | CCIE_RS] loop in network? >>>>>> >>>>>> All, >>>>>> >>>>>> So i have this network, and i am thinking i have a loop. I'm just not >>>>>> sure where or how. >>>>>> And i think it started happening after i created vlan interfaces in all >>>>>> vlans on all switches. So Cat1 is having vlan14,vlan567 and vlan69 >>>>>> interfaces and all the other switches in similar. >>>>>> >>>>>> They are NM16ESW cards, but IEEE stp is running so a Layer2 loop should >>>>>> be out of the question. Could i still have a routing loop? >>>>>> I am running OSPF in one giant area 0. >>>>>> >>>>>> How would i go about solving it? I can't use split horizon as OSPF >>>>>> doesn't use that. Should i artificially set routes such that they get a >>>>>> lower metric and manipulate things like that? >>>>>> >>>>>> I attached a small picture to clarify (this is taken from the Security >>>>>> lab Day4 VoD btw). >>>>>> Mind you, it might be something different entirely although i don't >>>>>> think so. >>>>>> >>>>>> But it's probably going to be something very stupid. And yes, i probably >>>>>> don't understand switching very well yet :-) >>>>>> >>>>>> Alef >>>>>> >>>>>> >>>>>> UHS Confidentiality Notice: This e-mail message, including any >>>>>> attachments, is for the sole use of the intended recipient (s) and may >>>>>> contain confidential and privileged information. Any unauthorized >>>>>> review, use, disclosure or distribution of this information is >>>>>> prohibited. If this was sent to you in error, please notify the sender >>>>>> by reply e-mail and destroy all copies of the original message. >>>>> >>>>> _______________________________________________ >>>>> For more information regarding industry leading CCIE Lab training, please >>>>> visit www.ipexpert.com >>>>> >>>>> Are you a CCNP or CCIE and looking for a job? Check out >>>>> www.PlatinumPlacement.com >>>>> >>> >>> > > _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com Are you a CCNP or CCIE and looking for a job? Check out www.PlatinumPlacement.com
