From: Terrence Rouse \(trouse\) (trouse@cisco.com)
Date: Sun Jul 18 2004 - 01:43:17 GMT-3
Thanks Brian,
That makes sense. I know what an "ENCAP FAILURE" is and I know all about
ARP. Well I thought I did :-). But I didn't check the ARP cache. I
thought I would have to get pass the encap failure before it would even
initiate and ARP request. IF it cant identify the interface how will it
know where to send the ARP out. And the CDP threw me off too.
Thanks for all the help.
T
-----Original Message-----
From: Brian McGahan [mailto:bmcgahan@internetworkexpert.com]
Sent: Saturday, July 17, 2004 10:43 PM
To: trouse@cisco.com; ccielab@groupstudy.com
Subject: RE: ENCAP FAILURES ON ETHERNET
"I am still not sure how I fixed it but I had some stuff messed up on the
3550 with my VLAN setup."
That is how you fixed it. Like Ken mentioned, encapsulation failure
means that the router doesn't know what layer 2 address to put in the
packet. If the next hop device was not within your broadcast domain (i.e.
wrong VLAN assignment) it would not have received your Ethernet ARP packet.
Furthermore it would not have been able to reply with its MAC address, so
the router initiating the ping packet wouldn't know what address to put in
the frame, hence encapsulation failure.
HTH,
Brian McGahan, CCIE #8593
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
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> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> trouse@cisco.com
> Sent: Saturday, July 17, 2004 8:34 PM
> To: ccielab@groupstudy.com
> Subject: ENCAP FAILURES ON ETHERNET
>
> I saw something today the blew my mind and time. Guess I always take
> ethernet for granted. But today i was getting encapsulation failure
on
> fastethernet. I had a ip addresss configure but it seems as if the
didnt
> recognize it as connected, however it showed up connected in ip route.
> The "sh int fa 0/0" was up/up. CDP was showing neighbor but I could
not
> pass ip traffic. I am still not sure how I fixed it but I had some
stuff
> messed up on the 3550 with my VLAN setup. And after sorting all this
out.
> Pings worked and encap failure went away. It was doing it on all my
> routers so I want to say it was the switch but....
>
>
> my question is: is there anyway the cat can cause the routers port to
> encap fail. I check the duplex/speed setting and all loooked find on
both
> ends but it was auto negotiated. If this had been my real lab I think
I
> would have cried. Spend over an hour before it finally started
working
> and this was a timed MOCK lab from NM (CheckIt). so I was pretty
> disappointed and upset that my time was wasted. Could this had been a
> bug?
>
> Of couuse the interface was "no shut" since I was getting CDP over it
and
> it saw the connected cat3550 switch.
>
> Thanks
> PUZZLED.....
>
>
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