From: Kenneth Wygand (KWygand@customonline.com)
Date: Sat Jul 17 2004 - 22:41:11 GMT-3
Hey PUZZLED... ;-)
"Encapsulation Failure" means that your configuration was missing a layer-3 to layer-2 mapping. On ethernet, this is your IP to MAC mappings in your ARP table. DId you perhaps have an ACL blocking ARP traffic? If you issue a
"debug arp" and then try your ping again, you can see if you are successfully resolving a MAC address from your IP address.
You will also get this a lot on ISDN if you don't have a layer-3 (IP address, for example) to layer-2 (phone number) mapping. The effects of this situation is that your ISDN line will come up, but pings across the line will fail (encapsulation failure, to be exact) ;-)
Hope this helps,
Ken
________________________________
From: nobody@groupstudy.com on behalf of trouse@cisco.com
Sent: Sat 7/17/2004 9:33 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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