Re: A noob issue about recursively routed

wandering_997 · ‎07-06-2009

Hi all,

Here's my configuration.

r2#show ip route

Gateway of last resort is not set

12.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 12.1.1.0/24 is directly connected, Serial1/0

S 12.1.1.1/32 [1/0] via 12.1.1.1

r2#

r2#show run int s1/0

interface Serial1/0

ip address 12.1.1.2 255.255.255.0

encapsulation frame-relay

end

r2#

r2#show run | include ip route

ip route 12.1.1.1 255.255.255.255 12.1.1.1

r2#

Let's ping 12.1.1.1 at r2, can r2 get the icmp reply from 12.1.1.1 ?

Why?

Wandering

dario.didio · ‎07-06-2009

Hi,

no, your ping will not work.

If you remove the static route, it will work.

reason is that if you ping 12.1.1.1, the static route will be used because it is more specific than the connected route. (sh ip route 12.1.1.1).

The destination for the static route is again 12.1.1.1, and the story goes on...

Why do you want to configure it like this?

HTH,

Dario

wandering_997 · ‎07-06-2009

Hi Dario,

Thank you for your reply.

Yes, you're right, it does't work.

This is not a requirement, but a accident of my colleague.

I didn't believe that untill I made a lab.

I'm wondering why it exists? It looks like a serious bug of routing mechanism.

And I made a /32 route to a host in the same segment on my laptop system, the host can be pinged successfully.

====

wandering@d630:~> route -n

Kernel IP routing table

Destination Gateway Genmask Flags Metric Ref Use Iface

10.217.15.11 10.217.15.11 255.255.255.255 UGH 0 0 0 eth0

10.217.15.0 0.0.0.0 255.255.255.0 U 1 0 0 eth0

127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 lo

0.0.0.0 10.217.15.1 0.0.0.0 UG 0 0 0 eth0

wandering@d630:~>

wandering@d630:~> ping -c 1 10.217.15.11

PING 10.217.15.11 (10.217.15.11) 56(84) bytes of data.

64 bytes from 10.217.15.11: icmp_seq=1 ttl=64 time=0.735 ms

--- 10.217.15.11 ping statistics ---

1 packets transmitted, 1 received, 0% packet loss, time 0ms

rtt min/avg/max/mdev = 0.735/0.735/0.735/0.000 ms

wandering@d630:~>

Why? Is IOS different from Unix like system?

Wandering