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New Member

Routing problem

HI Pradeep,

. There are three router A, B, C. A router having internet access and router A to B one Point to point Leased line, Router B to C one point to point Leased line.

Router C

One default router

Ip route 0.0.0.0 0.0.0.0 router B interface IP

Router B

IP route 0.0.0.0 0.0.0.0 Router A interface IP

IP route router C LAN network Router C serial int IP

Router A

IP route 0.0.0.0 0.0.0.0 ISP gateway.

This is our configuration.

I am able to ping Router C LAN IP from Router A

I am able to ping Router A and Router C LAN ip from Router C

I am able to ping Router B LAN ip and Loopback IP, but unable to ping Router A IP from Router C that is my problem , there is no dynamic routing protocol only default and static,

Please posted your Ideas for this

1 ACCEPTED SOLUTION

Accepted Solutions
New Member

Re: Routing problem

Hi,

As mentioned in previous post there is problem in your config.

RtrA dont have any information regarding C. Try to ping RtrB interface-ip add which is conneted to RtrC. Also try extended ping test from RtrA where you mention src-intrf which is connected to B. Here the ping will fail. The reason is the destination is not present in your routing table.

You said that you are able to ping from RtrC to RtrA while you are unable to ping from RtrA to RtrC which is highly impossible unless and untill you are have changed the src interface.

HTH

Cheers,

Nikhil E.

16 REPLIES

Re: Routing problem

On the router A,

- add route for the Router C LAN IP subnet and

- also for the Serial interface IP subnet ,

both pointing towards router B.

New Member

Re: Routing problem

What about defoult gateway on every one.(A,C)

Re: Routing problem

On the router A:

IP route serial_A->B

IP route serial_A->B

New Member

Re: Routing problem

Thiru,

From yur OP:

"I am able to ping Router A ... from Router C."

"I am ... unable to ping Router A IP from Router C that is my problem"

These two statements directly contradict each other.

Based on what you said in your OP, router A would have a routing table that looked like this:

C subnet to ISP -> directly connected

C serial net from A to B -> directly connected

S 0.0.0.0 0.0.0.0 -> ISP's router IP address

If you tried to ping router C's LAN interface it would send the packet to your ISP because that's the only route that matches in your routing table.

I believe what dhananjoy proposed should solve your problem.

HTH

New Member

Re: Routing problem

I am able to ping router C from router A but unable to ping router A from router C.

New Member

Re: Routing problem

On the router A:

IP route serial_A->B

IP route serial_A->B

Router A:

Ip route < router c LAN> serial A-B

Ip route < router c serial> serial A-B

Ip route 0.0.0.0 0.0.0.0 internet gateway

Router B

Ip route 0.0.0.0 0.0.0.0 serial B-A

Ip route < router c LAN> serial B-C

Router C

Ip route 0.0.0.0 0.0.0.0 serial C-B

Please find the routing information .

From Router B

I am able to ping internet and router C LAN IP's

From Router A

I am able ping internet and router C LAN IP's

From Router C

I am able to ping Router B serial IP but unable to ping internet and Router A

I am suspecting problem with router B, please any one help me

Blue

Re: Routing problem

Thiru:

Dont be so mysterious. Just give is the uncensired config. Your fill-ins are confusing.

Show us the addresses as they really are....

Victor

New Member

Re: Routing problem

You second post shows a different configuration than you stated in the OP. I agree with Victor, post the real sanitized configs.

New Member

Re: Routing problem

Let me get this straight you can ping router b from router c correct nut cannot ping router a from c

a--b ok b--c ok a--c error

make sure rtra has next hop route to c meaning a and b directly connected Ex

rta 10.10.10.1 rtrb 10.10.10.2

rtrb 20.20.20.1 --> rtrc20.20.20.2

ip route 10.10.10.1 255.255.255.0 20.20.20.1

make sure you get return traffic from c to a .HTH

New Member

Re: Routing problem

Does rtr c have a return route for rtra also could you post the router table from a b c

New Member

Re: Routing problem

a--b ok b--c ok a--c error ( correct )

I am facing problem when i am ping Router A from Router C .

New Member

Re: Routing problem

It appears that C does not have a return path for RTRA can you post the route table on RTRC.You are using static routes only correct

New Member

Re: Routing problem

Yes i am using only static routes

Silver

Re: Routing problem

On router A you have to configure the returnpath for routerC-LAN, without this returnpath router A will send all his traffic to ISP.

You say in your original post, router A can ping to router C, but router C can not ping to router A. Maybe router C address also can be found on ISP side, that's why router A got ping responses (something else is answer)

I suggest you post your configs and the result of "show ip route" for your three routers.

New Member

Re: Routing problem

Hi,

As mentioned in previous post there is problem in your config.

RtrA dont have any information regarding C. Try to ping RtrB interface-ip add which is conneted to RtrC. Also try extended ping test from RtrA where you mention src-intrf which is connected to B. Here the ping will fail. The reason is the destination is not present in your routing table.

You said that you are able to ping from RtrC to RtrA while you are unable to ping from RtrA to RtrC which is highly impossible unless and untill you are have changed the src interface.

HTH

Cheers,

Nikhil E.

New Member

Re: Routing problem

routing problem was fixed. I have added one route in router A

Ip route ( Router c Serial IP) ( Mask) ( Serial IP for router A-B). It everything working fine thanks a lot .

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