Lou,
Nothing to say you can't have an Ethernet link that is in fact
point-to-point. However, the router still needs a MAC address to get to
the router on the opposite side, due to the frame structure of
Ethernet. He will still need to ARP for a MAC address, and if there's no
next-hop IP address specified in the IP route statement the only address
the router can ARP for is the destination IP address in each packet
forwarded. So your ARP cache will still fill up with redundant entries.
It is always a design decision, but the art consists in understanding the
impacts your decisions may have down the road. The least obvious impacts
are the ones that are the most difficult to troubleshoot when things go
very wrong.
Understand that when the router uses up all its memory for ARP cache it
spontaneously reboots. This can be an extremely disruptive event on a busy
network, and most layer-three guys are not oriented toward checking the
size of the ARP cache to troubleshoot what appears to be an IOS instability
or maybe a hardware bug. Just a word to the wise.
Pamela
At 02:32 AM 12/30/00 -0600, Lou Nelson wrote:
>Cory,
>I read thru the responses and they are all good.... but I would like to
>add...
>Who is to say that an Ethernet interface is not a point to point. Using
>media converters changing a FE interface from tx to fiber and then back
>again I have many WAN FE point to point interfaces.
>In a few cases I prefer the interface because it prevent routing loops when
>links fail. I run HSRP on three gateway 7507s with gig uplinks to a 7513.
>The 3 7507 are logically connected via ATM interfaces that also house the
>HSRP. By using the interface to point out the gig links versus the opposite
>end ip interface on the gig link I prevent on 7507 believing that sending
>packets back to the originating router is a preferred EIGRP route to get to
>the 7513.
>
>
>So the Eth interface does not have to be a broadcast environment... it can
>be a point to point!
>
>-----Original Message-----
>From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
>Stull, Cory
>Sent: Friday, December 29, 2000 11:31 AM
>To: '[EMAIL PROTECTED]'
>Subject: ip route question
>
>
>
>I know I'm showing my ignorance here but I'm tired of trying to find the
>answer on CCO. Must be looking in the wrong places.
>
>
>I just saw a Boson question asking about ip route 0.0.0.0 0.0.0.0 int
>ethernet0
>
>
>I thought you could only point static routes like that out of point to point
>interfaces? For example: ip route 0.0.0.0 0.0.0.0 int ser0
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