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New Member

problems with static default next hop

I have an 891 router and I am configuring a static default pointing out one of the WAN links.  The problem is, specifying a next hop of the wan interface (Fa8 in this case) does not work.  However, specifying a next hop of DHCP works perfectly.

ip route 0.0.0.0 0.0.0.0 fastethernet8  (no work)

ip route 0.0.0.0 0.0.0.0 dhcp  (works)

Why would this be?

Thanks,

-J

1 ACCEPTED SOLUTION

Accepted Solutions

Re: problems with static default next hop

I think the reason for the default route statement with a physical interface not working is that the upstream router is not sending any proxy-arp for the ip addresses you are requesting arp for.

In simple words, If you set up a default route to physical interface and you are trying to reach 4.2.2.2 , your router will look into its routing table and will not find any route for it other than a default route pointing to Fethernet 8, so it will think that 4.2.2.2 is directly connected to it from that interface and will try ARP for 4.2.2.2 , having not recieve anything than from the upstream router ( which is not sending any proxy-arp ) it will just drop it as it will not be able to make a frame for that address 4.2.2.2.

hope i am making any sense here

Manish

9 REPLIES

Re: problems with static default next hop

Your configuration guide is here:

http://www.cisco.com/en/US/customer/docs/routers/access/800/860-880-890/software/configuration/guide/routconf.html#wp1148394

The guide says:

ip route prefix mask {ip-address | interface-type interface-number [ip-address]}

Try doing:

ip route 0.0.0.0 0.0.0.0 fastethernet 8

That should work.


Cheers, rate if this helps!

Tim

New Member

Re: problems with static default next hop

Yep Yep... that's exactly what I did.  It doesn't work if you specify a next hop of a physical interface. It takes the command, shows the command in the config, but won't route.

-J

Re: problems with static default next hop

And FA8 is set as a non-switchport, right?

New Member

Re: problems with static default next hop

sure is... it's one of the two wan ports on the router.  The 891 has two WAN interfaces.  Fa8 and Gig0.

-J

Re: problems with static default next hop

By next hop of physical interface , you mean the exit interface of the router right ?

manish

New Member

Re: problems with static default next hop

Yes, that is correct, Fa8 is the exit interface on the router.  The 891 has switchports Fa0-7 and wan interfaces fast 8 and gig 0.

-J

Re: problems with static default next hop

I think the reason for the default route statement with a physical interface not working is that the upstream router is not sending any proxy-arp for the ip addresses you are requesting arp for.

In simple words, If you set up a default route to physical interface and you are trying to reach 4.2.2.2 , your router will look into its routing table and will not find any route for it other than a default route pointing to Fethernet 8, so it will think that 4.2.2.2 is directly connected to it from that interface and will try ARP for 4.2.2.2 , having not recieve anything than from the upstream router ( which is not sending any proxy-arp ) it will just drop it as it will not be able to make a frame for that address 4.2.2.2.

hope i am making any sense here

Manish

New Member

Re: problems with static default next hop

ahhhh... you may be correct here.  There is a no proxy-arp set on the dhcp gateway address. I will need to test this tomorrow am (as it's a production net)  thanks for the tip, I'll let you know how it works.

-J

New Member

Re: problems with static default next hop

yep, that was the problem.  Removing proxy-arp solved it.

-J

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