From: Michael Zuo (mzuo@ixiacom.com)
Date: Sat Jan 27 2007 - 22:11:33 ART
I checked the following items and they all seemed OK:
1. all trunk interfaces are "trunking" under "show int trun"
2. vlan 30 is configured on both CAT1 and CAT2
3. all used interfaces are "FWD" under "show span vlan 30"
4. all interfaces are full duplex and 100 mbps under "show interface"
I turned on "deb arp" on devices and noticed that:
1. when R4 is pinging CAT1, CAT1 does not see any ARP request
2. when CAT1 is pinging R4, R4 sees the ARP requests and responds, but CAT1 does not see the response comes back
This seems that communication from R4 to CAT1 is blocked somehow. Any suggestions?
I also put in a temporary vlan 30 interface on CAT2, R4 can ping CAT2, R3 can be ping CAT1, but just not across the trunk link which seems to be cause. But I don't know why this is happening...
Thanks in advance ....
-----Original Message-----
From: Muizebelt Danny [mailto:Danny.Muizebelt@osiatis.at]
Sent: Thursday, January 25, 2007 1:12 AM
To: Michael Zuo; ccielab groupstudy
Subject: RE: ICMP showing encapsulation failed
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256
I think you didn't get an arp resolution for the 172.16.34.4 address, that's why the encapsulation failed because there is no L3 to L2 mapping.
The reason why there is no arp resolution could be a problem with your trunk, is it up? Is vlan 30 defined on both switches? Is the spanning tree working properly?
Another thing I wanted to point out, if you statically configure duplex settings on one side and leave the other side on auto then the auto side will fall back to default half-duplex. Statically configuring duplex settings switches off the auto negotiation. So either both sides on auto or both statically configured.
Danny Muizebelt
CCIE #17353
- -----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Michael Zuo
Sent: Donnerstag, 25. Jdnner 2007 08:22
To: ccielab groupstudy
Subject: ICMP showing encapsulation failed
Hi group,
I am scratching my head on this one (probably something basic), please
help! And thanks in advance....
R3(f0/1)---------(f0/4)CAT1(f0/14)-----------(f0/14)CAT2(f0/5)----------
- -----R4(f0/0)
When I ping from R3 to R4, I get encapsulation failed message on R3:
R3(config-if)#do ping 172.16.34.4
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.34.4, timeout is 2 seconds:
2d07h: IP: tableid=0, s=172.16.34.3 (local), d=172.16.34.4
(FastEthernet0/1), ro
uted via RIB
2d07h: IP: s=172.16.34.3 (local), d=172.16.34.4 (FastEthernet0/1), len
100, send
ing
2d07h: IP: s=172.16.34.3 (local), d=172.16.34.4 (FastEthernet0/1), len
100, enca
psulation failed.
2d07h: IP: tableid=0, s=172.16.34.3 (local), d=172.16.34.4
(FastEthernet0/1), ro
uted via RIB
2d07h: IP: s=172.16.34.3 (local), d=172.16.34.4 (FastEthernet0/1), len
100, send
Ing
Configuration:
R3:
=======
R3(config-router)#do sh run int f0/1
Building configuration...
Current configuration : 96 bytes
!
interface FastEthernet0/1
ip address 172.16.34.3 255.255.255.0
duplex auto
speed auto
end
R3(config-router)#
CAT1:
========
CAT1(config)#do sh run int f0/4
Building configuration...
Current configuration : 97 bytes
!
interface FastEthernet0/4
switchport access vlan 30
switchport mode access
duplex full
end
CAT1(config)#do sh run int f0/14
Building configuration...
Current configuration : 137 bytes
!
interface FastEthernet0/14
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 1,20,30,40
switchport mode trunk
CAT1(config-if)#do sh run int vlan 30
Building configuration...
Current configuration : 63 bytes
!
interface Vlan30
ip address 172.16.34.10 255.255.255.0
end
CAT2:
CAT2(config-if)#do sh run int f0/5
Building configuration...
Current configuration : 97 bytes
!
interface FastEthernet0/5
switchport access vlan 30
switchport mode access
duplex full
end
CAT2(config-if)#do sh run int f0/14
Building configuration...
Current configuration : 137 bytes
!
interface FastEthernet0/14
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 1,20,30,40
switchport mode trunk
end
CAT2(config-if)#
R4
=======
R4(config-router)#do sh run int f0/0
Building configuration...
Current configuration : 96 bytes
!
interface FastEthernet0/0
ip address 172.16.34.4 255.255.255.0
duplex auto
speed auto
end
R4(config-router)#
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