Hello If R1 send a frame with the DE bit set and router acting as frame-relay switch is really working as a switch frame-relay, it only changes the dlci number ( if needed ) and forward the frame to the output interface, it must keep DE, BECN and FECN bit as arrived, in this case the frame going out from the switch must have the DE bit set. If, as I'm afraid, router acting as frame-relay switch in not working as switch, it must read the packet at level three and forward the packet to the output interface creating a totally new frame without considering the original frame ( at level 2 ), so DE bit is not set because router is not configured for that. Normally, this type of forwarding is done using policy-routing, but don't forget that policy-routing also decrement TTL and don't forward a packet if arrive with TTL 1.
This must be a explanation to why you see three hops in traceroute, but if this is true the router acting fr-switch has the same ip address that R3......Who provide the ip addresses for the exercise? If they are invented by you, my theory is not valid. In another case it could be a trick of the person who created the exercise. Finally, you can see if the frame arrived with the DE bit set with show frame-relay pvc. Rafa -----Mensaje original----- De: Priscilla Oppenheimer [mailto:[EMAIL PROTECTED]] Enviado el: miircoles 21 de agosto de 2002 19:40 Para: [EMAIL PROTECTED] Asunto: RE: Traceroute IP displays twice (previous post by [7:51823] Thanks for the ideas. I did try some of those things. I didn't know that you could tell if a device was a Frame Relay switch or router based on whether it sets the DE bit, though? And how would I know if the frame arrived with the DE bit set?? This was on a virtual lab. I didn't have access to the FR switch. I agree with you that it was acting funny. If I have time I'll go back and do some more testing, but I can't promise that I will have time. Thank-you very much for your inteest in the problem and your suggestions, though. Priscila [EMAIL PROTECTED] wrote: > > Hi Priscilla > > Can you put debug ip icmp in both R1 and R3 routers? or better > debug ip > packet detail. This is for checking if R3 is really sending six > icmp ttl > exceeded when traceroute is executed. > > Also, you can use ping with record option set instead > traceroute to see the > path. > > I'm suspecting that frame-relay switch is not configured with > frame-relay > switching, but this introduce several issues about ospf. Can > you check with > show ip ospf database that you have only three routers.? Also > you can check > if frame-relay switch router is really working as a switch > frame-relay > sending traffic from R1 marked with DE. If this arrive to R3 > without DE mean > that frame-relay switch is really routing ip traffic instead of > switching > frames. The same test must be done between R2 and R3 > > Another test should be send pings from 172.16.1.1 to > 172.16.2.2 with ttl > set to 1, 2 and 3. Debug ip packet detail in all routers must > help you to > identified what is wrong > > Is cdp active ? If yes, can you check neighbours of R3? You > must see only R1 > and R3 is router acting as fr-switch is working properly. > > > Please, could you update me with result of this issue ? I'm > very interesting > whit it. > > Regards > > Rafa > > > > -----Mensaje original----- > De: Priscilla Oppenheimer [mailto:[EMAIL PROTECTED]] > Enviado el: lunes 19 de agosto de 2002 20:27 > Para: [EMAIL PROTECTED] > Asunto: RE: Traceroute IP displays twice (previous post by Pri > [7:51633] > > > Hi Mark, etc. > > I never got a satisfactory explanation for my results with > Trace Route. In > my case, a particular router was claiming to be the first hop > and the second > hop. That's different from what we're seeing in the current > question, where > two different routers are claiming to be the first hop (due to > load > balancing). > > Here are the syptoms: > > 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.) > > 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 > > > Vicuna, Mark wrote: > > > > While we are on the topic.. I remember a post by Priscilla a > > few months > > ago now (I think) with a traceroute showing 2 path entries of > > the same > > ip. The result of the traceroute was not able to be > reproduced > > (I > > think). Anyone remember what the outcome of this was? > > > > > > The archives are not searchable at this point in time. > > > > > > Cheers > > Mark. > > > > > -----Original Message----- > > > From: Robert D. Cluett [mailto:[EMAIL PROTECTED]] > > > Sent: Monday, 19 August 2002 19:10 > > > To: [EMAIL PROTECTED] > > > Subject: Re: traceroute IP displays twice [7:51622] > > > > > > > > > Thanks Raj! > > > > > > ""Raj Santiago"" wrote in message > > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > > i should have included this part as well to the previous > > post : > > > > > > > > >1 172.26.1.13 20 msec > > > > 172.26.1.2 20 msec > > > > 172.26.1.13 20 msec > > > > > > > > The above indicates, of the two possible paths the router > > > has [172.26.1.2, > > > > 172.26.1.13] it has chosen the path 172.26.1.13. > ********************************************** > Noticia legal > Este mensaje electrsnico contiene informacisn de BT Ignite > Espaqa S.A.U. que > es privada y confidencial, siendo para el uso exclusivo de la > persona (s) o > entidades arriba mencionadas. Si usted no es el destinatario > seqalado, le > informamos que cualquier divulgacisn, copia, distribucisn o uso > de los > contenidos esta prohibida. Si usted ha recibido este mensaje > por error, por > favor borre su contenido lo antes posible. > Gracias. ********************************************** Noticia legal Este mensaje electrsnico contiene informacisn de BT Ignite Espaqa S.A.U. que es privada y confidencial, siendo para el uso exclusivo de la persona (s) o entidades arriba mencionadas. Si usted no es el destinatario seqalado, le informamos que cualquier divulgacisn, copia, distribucisn o uso de los contenidos esta prohibida. Si usted ha recibido este mensaje por error, por favor borre su contenido lo antes posible. Gracias. 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