From: tan (tan@dia.janis.or.jp)
Date: Fri Feb 07 2003 - 04:04:11 GMT-3
Static out interface usually implies last stop before host. It says "hey, I
know all the hosts are directly connected to me, so I will arp for its MAC
address".
If your forwarding router doesn't know that the destination network is still
one or more hops away, and if you have a static to interface route, it will
think all hosts are sitting on the shared cabling out the interface and arp
for it everytime. The real host can't answer obviously, but if the next hop
has proxy arp on, AND there are appropriate routes in its table, an arp
reply will come. If no arp reply comes back, then proxy arp is not on. Or
none of the routers sharing the link have the destination network in their
tables.
Is this some manipulated practice scenario? But then static routes are
usually forbidden anyway including static to interface. One red flag with
using static to interface is looking for restrictions on route exchanging
between downstream routers, or flapping routes way downstream that also flap
on and off in next hop's table (meaning losing the requirement needed for
proxy arping back). Even if the route is down, you may still want to forward
the packet as far as it can go because next router or next next router may
have backup plan to deal with it, rather than drop it because failed proxy
arp.
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> Neil G. Legada
> Sent: Friday, February 07, 2003 12:08 PM
> To: ccielab@groupstudy.com
> Subject: Default route pointing to an interface or next hop IP address
>
>
> Hello group,
>
> Until I now couldn't understand why a default or static route
> doesn't always
> work when pointing to an interface. Been a victim of this a few times
> wherein during the staging process it works but on the actual
> implementation
> it doesn't (on some instance it worked). Is there a hard
> written rule here
> when to use the physical interface or not on a certain scenario ??? I
> usually encounter this problem with DDR (physical/dialer
> interfaces) or HSRP
> on LAN's. Am I right to say here that when using the physical
> interface
> instead of the next hop IP address, the router would do an
> extra sort of an
> ARP-ing process to resolve the next hop address ???
>
> Appreciate any feedback.
>
>
> Kind regards,
> Neil
> .
.
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