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
