From: Fahad Khan (fahad.khan@gmail.com)
Date: Tue Oct 21 2008 - 04:25:10 ARST
The routing loop is being occured in between R3 and R5
R3 : D EX 6.6.1.0 [170/2425856] via *6.6.35.5*, 00:01:37,
Serial1/0.35 -----> next hop is R5
[170/2425856] via 6.6.13.1, 00:01:37, Serial1/1
R5 : D EX 6.6.1.0 [170/2937856] via *6.6.35.3*, 00:01:23,
Serial1/0.53 ------> next hop is R3
The problems like routing loops and route feedback are handled by
1- Tagging
2- Modifying AD
3- Modifying Metric
Ist solution:
On R4, set a tag when redistribution is done from EIGRP to OSPF and On R5 ,
configure NOT to send the tagged routes back to R3.
2nd solution: (modifying AD seems not possible in this case; since In eigrp
we cant modify specific external routes)
well,
On R3 , see if you can modify the AD of the route coming from R5 (distance
180 x.x.x.x 0.0.0.0 <acl>)
(lab it n tell us)
HTH
best regards,
On 10/21/08, Ahsan Mohiuddin <ahsan.mohiuddin@gmail.com> wrote:
>
> Here's the topology:
>
> R1---R3----R4
> | |
> R5----R6
>
> All links are frame-relay P2P, except R1-R3 which is HDLC serial.
>
> (1) R1 is advertising its Lo0 int (6.6.1.1/24) in RIP. R1 is also running
> EIGRP 100 and redistributing RIP into EIGRP 100.
> (2) R1 & R3 are EIGRP neighbors over serial link (6.6.13.0/24).
>
> (3) R3 is learning the route to 6.6.1.0/24 via 6.6.13.1:
>
> D EX 6.6.1.0 [170/2425856] via 6.6.13.1, 00:00:02, Serial1/1
>
> R3 is able to ping destination 6.6.1.1:
>
> Sending 5, 100-byte ICMP Echos to 6.6.1.1, timeout is 2 seconds:
> !!!!!
> Success rate is 100 percent (5/5), round-trip min/avg/max = 4/12/32 ms
>
> (4) R3 is advertising this route to its EIGRP 100 neighbors R4 & R5.
>
> At R4:
> D EX 6.6.1.0 [170/2937856] via 6.6.34.3, 00:07:26, Serial1/0.43
> At R5:
> D EX 6.6.1.0 [170/2937856] via 6.6.35.3, 00:01:23, Serial1/0.53
>
> (5) R4, R5, R6 are running in OSPF Area 0. Note that R4 & R5 do not have a
> direct link, and both these routers are OSPF neighbors to R6.
> (6) Now on R4, we configure redistribution of EIGRP 100 into OSPF. As a
> result, R6 learns the route 6.6.1.0/24:
>
> O E2 6.6.1.0 [110/20] via 6.6.46.4, 00:03:06, Serial1/0.64
>
> (7) R6 advertises this route to R5. As a result, R5 removes it original
> route (distance 170) and installs O E2 (distance 90) route:
>
> O E2 6.6.1.0 [110/20] via 6.6.56.6, 00:00:01, Serial1/0.56
>
> (8) We configure R5 to redistribute OSPF into EIGRP 100. This causes R3 to
> learn an additional path to 6.6.1.0/24:
>
> At R3:
> D EX 6.6.1.0 [170/2425856] via 6.6.35.5, 00:01:37, Serial1/0.35
> [170/2425856] via 6.6.13.1, 00:01:37, Serial1/1
>
> (9) Now at R3, if we ping 6.6.1.1..
>
> Sending 5, 100-byte ICMP Echos to 6.6.1.1, timeout is 2 seconds:
> .....
> Success rate is 0 percent (0/5)
>
> *TASK*
> Ensure that R3 can reach 6.6.1.0/24. Do not disable CEF on R3. Do not
> create
> any tunnels. You are allowed to change IP Addressing on a single link
> (subnet) in the topology.
>
>
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-- Fahad KhanBlogs and organic groups at http://www.ccie.net
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