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routing issue





All the routers are conncected using serial links.

RTR A is running Eigrp and RTRB, RTR C and RTR D are running ospf. /8 network is used on RTR A and RTR E whereas /8 is used on the remaining Routers.

I am trying for redundency in this scenario.

My problem is, / 25 network is allocated to RTR D. is allocated to ATM machine.

RTR E is the backup for this ATM machine( VSAT connectivity).

Whenever serial link b/n RTR C and RTR D goes down , then traffic should take path through RTR E.(i.e RTR A to RTR E to reach ATM on VSAT link).

I have configured the following routes on RTR A which is running Eigrp.

ip route

ip route 120.

Where is serial ip of RTR B and is serial ip of RTR E.

As soon as I shutdown the serial link of RTR C which is connecting to RTR D , we are getting ospf updates till RTR B.Where as the static route configured on the RTR A is not purging out from RTR A route table so that floating static route will come in to picture.

static routes are redistibuted on RTR A and RTR B under Eigrp (RTR A) and OSPF (RTR B).

Whenever I shutdown serila link of RTR C , ospf updates on RTR B , RTR C are not showing subnet and static route on RTR A is still pointing towards RTR B not to RTR E.

But as soon as i shut the serial interface of RTR C , the static on RTR A is not vanishing from routing table of RTR A.

The ouptut taken on RTR A and RTR B without shutting down the serail link of RTR C are.

RTR A#sh ip route

Routing entry for

Known via "static", distance 1, metric 0 (connected)

Redistributing via eigrp 15

Advertised by eigrp 15

Routing Descriptor Blocks:


Route metric is 0, traffic share count is 1


RTR B#sh ip route

Routing entry for

Known via "ospf 192", distance 110, metric 1954, type inter area

Redistributing via rip

Advertised by rip metric 10

Last update from on GigabitEthernet5/2, 00:00:31 ago

Routing Descriptor Blocks:

*, from, 00:00:31 ago, via GigabitEthernet5/2

Route metric is 1954, traffic share count is 1

As soon as i make the serial link of RTR C which is connecting to RTR D , the above route to should go off and floating static route should be prrsent in the routing table of RTR A which is not happening in this case.

What could be the problem.How to achieve redundency in this case.

Any help would be appreciated.


Re: routing issue

The config on RTR A is

RTRA#router eigrp 15

redistribute static


no auto-summary

eigrp log-neighbor-changes

and routes added on RTRA

ip route

ip route 110

Note that RTR B is running OSPF and is allocated to OSPF network.

Re: routing issue


Configure the serial link between RTR A & RTR B to run OSPF. Just configure a floating static route for this network on all the routers to point to the alternate path via RTR A-->RTR E.

This way, RTR A would learn via OSPF from RTR B and when RTR A stops learning the OSPF route from RTR B the floating static route on RTR A will come into the routing table. RTR B & RTR C would act the same way as they would forward the traffic via RTR A if the route via RTR D becomes unavailable.




Re: routing issue

HI Sundar ,

Thanks for your reply and help.

I configured the serail link b/n RTR A and RTR b to run ospf and traffic is diveretd through RTR E as soon as I shut doen the serial link of RTR C connecting to RTR D.

If u have time then can you give some tips for preparing CCIE R & S exam.



Re: routing issue


Glad to hear it helped and thanks for the rating!!

Here's a good link that provides preparation outlines and general resources for R&S Lab.

Another thing I would recommend is sign up for CCIE groupstudy ( newsgroup, if you haven't already done that, and that will be of tremendous help in your preparation. Feel free to post any specific questions you may have and I shall try to respond to it promptly.

Good Luck!!




Re: routing issue

Hi Sundar ,

Thanks for your valuable info.

The previous problem is sorted out and I have a doght from the above setup.

RTRA(eigrp)-RTRB(a0)-RTRC(a0+a66)|-RTRD(a66) |-RTDE(a66)



So many locations are connected to RTR C and each and every location has one ATM machine.

One tandem server is connected to RTR A and other one is connected to RTR B. RTR D to RTR G and other location ATM machines are interacting with Tandem server located at RTR B.

We are doing testing by taking RTR D ATM machine which should connect to Tandem server located at RTR A.

Tandem server ip which is connecting to RTR A is and which is connecting to RTR B is

If i want to connect to from RTR D atm machine i need to do the following changes.

1. add a host route ( )with next hop pointing to RTR A serail ip.

2.Configure a static nat on RTR A and apply it on ethernet and serial interface.

Problem is as soon as i add static route for on RTR B all the ATM machines are communicating with RTR A tandem server.

I want RTR D ATM machine should comunicate with RTR A's tandem server and remaining locations(RTR E , RTR F and so on)should comunicate with RTR B's tandem server.

How can i accomplish this.

Many thanks in advance.


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