At 9:47 PM -0400 6/28/02, Priscilla Oppenheimer wrote: >Thank-you very much for going to that effort! Thanks to everyone who >replied, in fact. I'm actually glad to hear that you can't reproduce the >problem. It confirms my belief that something very strange is happening. Of >course, it could easily turn out to be some dumb thing on my part too. ;-) > >There may be something weird with the DLCIs and the switch. I don't have >access to the switch. There seem to be many DLCIs.
In each pod, there are four routers with frame physical interfaces. There are two VCs between each of the routers, one with the router as the hub and one as a spoke. In other words, from R2 to R3, DLCI 223 assumes R2 is the hub, and DLCI 233 assumes R3 is the hub. >I tried turning off >Inverse ARP hoping my routers wouldn't learn about them, but they did >anyway. But the ones they learned about that weren't actually in use were marked UNUSED, albeit ACTIVE. It's actually a switch cloud, with four interlinked 7000's servicing the various pods. The inter-router frame connections are pure frame (DTE-DCE rather than NNI, but I need to check). I am copying Curt, who actually designed the frame service. I may not be able to get answers until Monday, as I'm changing my access to the backbone. No routing is involved in the frame system, although these backbone routers do run routing for other functions. > >Well, I used up my time on the lab rack for now, but I'll do some more >research. Thanks again for your help. > >Priscilla > >At 07:48 PM 6/28/02, [EMAIL PROTECTED] wrote: >>P: Repeated your setup with configurations for serial lines, and OSPF >>starting from clean configs. I could not duplicate your results. All my >>traces were as expected. Trace from r2 to r1 shown, reverse direction is >>similiar. >> >>r2#trace 172.16.1.1 >> >>Type escape sequence to abort. >>Tracing the route to 172.16.1.1 >> >> 1 172.16.2.3 12 msec 12 msec 12 msec >> 2 172.16.1.1 24 msec 20 msec * >> >>My frame switching router is configured for a full mesh. I >>checked that only the configured dlci's between r1-r3, and r3-r2 were >>used (there is an active dlci between r1 and r2 but the packet count is >>0). The frame-switch shouldn't be configured with IP addresses and won't >>decrement TTL. >> >>Can't explain it, can't repeat it. I'm using IOS 12.1. Suggest you try >>and repeat with another setup. >> >> >>Fred >> > >> > From: "Priscilla Oppenheimer" >> > Date: 2002/06/28 Fri PM 01:55:12 EDT >> > To: [EMAIL PROTECTED] >> > Subject: Re: extra hop [7:47625] >> > >> > At 10:23 PM 6/27/02, Priscilla Oppenheimer wrote: >> > >Hello Group Study, >> > > >> > >Any ideas on why a router would show up twice in a trace route? >> > > >> > >r1#trace 172.16.2.2 >> > > >> > >Type escape sequence to abort. >> > >Tracing the route to 172.16.2.2 >> > > >> > > 1 172.16.1.3 12 msec 12 msec 12 msec >> > > 2 172.16.1.3 12 msec 8 msec 8 msec >> > > 3 172.16.2.2 24 msec 20 msec 20 msec >> > > >> > >It's a frame-relay hub-and-spoke topology. I'm on one spoke trying to >> trace >> > >to another spoke through the hub. The trace succeeds. The network is >> > >working, but what's with the router replying twice? (It happens if I >> go the >> > >other way too.) >> > >> > Nobody answered!? ;-) Actually, in some ways that's good. It confirms my >> > belief that what I'm seeing is bizarre. >> > >> > I am using a Gettlabs rack. The Gettlabs service is very cool, by the >way, >> > with multiple routers and interfaces of all sorts. >> > >> > The Frame Relay "cloud" is implemented by a Cisco router acting as a >Frame >> > Relay switch, I believe. I don't have access to it. >> > >> > However, and I know this is going to sound wrong, but after much >> tinkering, >> > I think the router acting as the FR switch is decrementing the TTL and >> > forwarding the packet. >> > >> > On my first set of traces, when the source sets the TTL to one, the >packet >> > makes it to the router across the cloud and the first router replies with >> > Dest Unreachable TTL expired. On the second set of traces, when the >source >> > sets the TTL to two, the packet still only makes it to the first router >> > across the cloud, which replies with Dest Unreachable TTL expired. >> > >> > The only explanation is that the switch decrements the TTL, then realizes >> > "hey, I'm a switch" and forwards the packet, even if the TTL is now zero. >> > Has anyone ever heard of a router acting as a FR switch doing that? Any >> > comments from Gettlabs folks (Howard?) >> > >> > Thanks >> > >> > Priscilla >> > >> > >> > >The hub router is 172.16.1.3. Why is it sending back the dest >unreachable >> > >twice? >> > > >> > >The topology is: >> > > >> > >R1------R3-----R2 >> > > >> > > >> > >Here are my configs: >> > > >> > >r1 >> > >ip subnet-zero >> > >no ip icmp rate-limit unreachable >> > >! >> > >interface Loopback0 >> > > ip address 192.168.255.1 255.255.255.255 >> > >! >> > >interface Ethernet0/0 >> > > description to Cat 5K 3/1 >> > > ip address 10.10.1.1 255.255.255.0 >> > > half-duplex >> > >! >> > >interface TokenRing0/0 >> > > description in ring 1 >> > > ip address 192.168.1.1 255.255.255.0 >> > > ring-speed 16 >> > >! >> > >interface Serial1/0 >> > > ip address 172.16.1.1 255.255.255.0 >> > > encapsulation frame-relay >> > > ip ospf network point-to-point >> > > frame-relay interface-dlci 133 >> > > frame-relay lmi-type ansi >> > >! >> > >router ospf 1 >> > > log-adjacency-changes >> > > network 10.10.1.0 0.0.0.255 area 0.0.0.0 >> > > network 172.16.0.0 0.0.255.255 area 0.0.0.0 >> > > network 192.168.1.0 0.0.0.255 area 0.0.0.0 >> > > network 192.168.255.1 0.0.0.0 area 0.0.0.0 >> > >! >> > >ip classless >> > > >> > > >> > > >> > >R3 >> > >ip subnet-zero >> > >no ip icmp rate-limit unreachable >> > >! >> > >interface Loopback0 >> > > ip address 192.168.255.3 255.255.255.255 >> > >! >> > >interface Ethernet0/0 >> > > description link to cat5k 3/3 >> > > ip address 10.10.3.1 255.255.255.0 >> > > half-duplex >> > >! >> > >interface Serial1/0 >> > > description Frame relay >> > > no ip address >> > > encapsulation frame-relay >> > > no fair-queue >> > > no frame-relay inverse-arp >> > > frame-relay lmi-type ansi >> > >! >> > >interface Serial1/0.1 point-to-point >> > > description link to R1 >> > > ip address 172.16.1.3 255.255.255.0 >> > > ip ospf network point-to-point >> > > frame-relay interface-dlci 331 >> > >! >> > >interface Serial1/0.2 point-to-point >> > > description link to R2 >> > > ip address 172.16.2.3 255.255.255.0 >> > > ip ospf network point-to-point >> > > frame-relay interface-dlci 332 >> > >! >> > >router ospf 1 >> > > log-adjacency-changes >> > > network 10.10.3.0 0.0.0.255 area 0.0.0.0 >> > > network 172.16.0.0 0.0.255.255 area 0.0.0.0 >> > > network 192.168.255.3 0.0.0.0 area 0.0.0.0 >> > >! >> > >ip classless >> > > >> > > >> > >R2 >> > >! >> > >hostname r2 >> > >! >> > >ip subnet-zero >> > >no ip icmp rate-limit unreachable >> > >! >> > >interface Loopback0 >> > > ip address 192.168.255.2 255.255.255.255 >> > >! >> > >interface Ethernet0/0 >> > > description to Cat 5K 3/2 >> > > ip address 10.10.2.1 255.255.255.0 >> > > half-duplex >> > >! >> > >interface TokenRing0/0 >> > > ip address 192.168.2.1 255.255.255.0 >> > > ring-speed 16 >> > >! >> > >interface Serial1/0 >> > > ip address 172.16.2.2 255.255.255.0 >> > > encapsulation frame-relay >> > > ip ospf network point-to-point >> > > no fair-queue >> > > frame-relay interface-dlci 233 >> > > frame-relay lmi-type ansi >> > >! >> > >router ospf 1 >> > > log-adjacency-changes >> > > network 10.10.2.0 0.0.0.255 area 0.0.0.0 >> > > network 172.16.0.0 0.0.255.255 area 0.0.0.0 >> > > network 192.168.2.0 0.0.0.255 area 0.0.0.0 >> > > network 192.168.255.2 0.0.0.0 area 0.0.0.0 >> > >ip classless >> > > >> > > >> > >There's a Cisco router "in the cloud" acting as a Frame Relay switch, >> > >switching from DLCIs. I don't have its config. (This was a virtual lab). >> > >Thanks for any hints you can give me. >> > > >> > >Priscilla >> > > >> > >________________________ >> > > >> > >Priscilla Oppenheimer >> > >http://www.priscilla.com >> > ________________________ >> > >> > Priscilla Oppenheimer >> > http://www.priscilla.com >________________________ > >Priscilla Oppenheimer >http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=47751&t=47625 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
