From: Brian McGahan (bmcgahan@internetworkexpert.com)
Date: Sun Jul 18 2004 - 04:24:10 GMT-3
Terrence,
"encapsulation failed" is an interface related message. This
means that the routing table lookup was successful and the outgoing
interface was chosen, but layer 2 resolution was not obtained on that
interface. If the router couldn't identify the outgoing interface you
would get the "unroutable" message.
Rack12R2#show ip route 1.2.3.4
% Network not in table
Rack12R2#ping 1.2.3.4
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.2.3.4, timeout is 2 seconds:
IP: s=150.1.2.2 (local), d=1.2.3.4, len 100, unroutable.
IP: s=150.1.2.2 (local), d=1.2.3.4, len 100, unroutable.
IP: s=150.1.2.2 (local), d=1.2.3.4, len 100, unroutable.
IP: s=150.1.2.2 (local), d=1.2.3.4, len 100, unroutable.
IP: s=150.1.2.2 (local), d=1.2.3.4, len 100, unroutable.
Success rate is 0 percent (0/5)
HTH,
Brian McGahan, CCIE #8593
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987 x 705
Outside US: 775-826-4344 x 705
24/7 Support: http://forum.internetworkexpert.com
Live Chat: http://www.internetworkexpert.com/chat/
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> Terrence Rouse (trouse)
> Sent: Saturday, July 17, 2004 11:43 PM
> To: 'Brian McGahan'; ccielab@groupstudy.com
> Subject: RE: ENCAP FAILURES ON ETHERNET
>
> 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
> Toll Free: 877-224-8987 x 705
> Outside US: 775-826-4344 x 705
> 24/7 Support: http://forum.internetworkexpert.com
> Live Chat: http://www.internetworkexpert.com/chat/
>
>
> > -----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.....
> >
> >
>
This archive was generated by hypermail 2.1.4 : Sun Aug 01 2004 - 10:11:58 GMT-3