Encapsulation Failed on Cisco 2651 Router

[ThVoipJakeT91]

Hi,

I have a Cisco 2651 Router and am trying to connect it to my Virgin Media Cable Internet service. Below is the current setup:

[Internet]  --> [Virgin Super Hub (192.168.100.1)] --> [(192.168.100.2) Cisco  2651 (192.168.40.1)] --> [(192.168.40.2) Laptop]

I am having  an absolute nightmare with it. I work at an Entanet and so have shown  the config to my colleagues and we just can't understand it. When  pinging the Superhub I get responses. However, when trying to ping  anywhere past the Superhub I get nothing other than 'Encapsulation  Failed'. I have tried putting the cisco onto my internal network (in the same way that the servers and PC's are connected) and again, I can ping the server hosting DHCP and all other servers and PC's in the internal network but nothing past the server hosting the DHCP.

Below  is the config as well as the results of the pings. I would extremely  appreciate any help as I'd rellay like to get into Cisco routers.

Thanks in advance.

Router-01#sr

Building configuration...

Current configuration : 1122 bytes

!

version 12.2

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption

!

hostname Router-01

!

!

no ip subnet-zero

!

!

no ip domain lookup

ip name-server 208.67.222.222

ip name-server 208.67.220.220

!

ip dhcp pool defaultpool

   network 192.168.40.0 255.255.255.0

   default-router 192.168.40.1

   dns-server 192.168.40.1

!

!

!

!

!

!

!

!

!

!

!

!

mta receive maximum-recipients 0

!

!

!

!

interface FastEthernet0/0

ip address 192.168.100.2 255.255.255.0

ip nat outside

duplex auto

speed auto

!

interface FastEthernet0/1

ip address 192.168.40.1 255.255.255.0

ip nat inside

duplex auto

speed auto

!

ip nat inside source list 1 interface FastEthernet0/0 overload

no ip classless

ip route 0.0.0.0 0.0.0.0 FastEthernet0/0

ip http server

!

!

access-list 1 permit 192.168.40.0 0.0.0.255

!

call rsvp-sync

!

!

mgcp profile default

!

dial-peer cor custom

!

!

!

alias exec s show ip int bri

alias exec sr show run

!

line con 0

exec-timeout 0 0

logging synchronous

line aux 0

line vty 0 4

password abc_123

login

line vty 5 15

password abc_123

login

!

!

end

--------------------------------------------------

--------------

When I attempt to ping 192.168.100.1

Router-01#debug ip packet
IP packet debugging is on
Router-01#debug arp
ARP packet debugging is on

Router-01#ping 192.168.100.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.100.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms
Router-01#
*Mar  1 00:07:16.498: IP: s=192.168.100.2 (local), d=192.168.100.1 (FastEthernet0/0), len 100, sending
*Mar  1 00:07:16.502: IP: s=192.168.100.1 (FastEthernet0/0), d=192.168.100.2 (FastEthernet0/0), len 100, rcvd 3
*Mar  1 00:07:16.502: IP: s=192.168.100.2 (local), d=192.168.100.1 (FastEthernet0/0), len 100, sending
*Mar  1 00:07:16.502: IP: s=192.168.100.1 (FastEthernet0/0), d=192.168.100.2 (FastEthernet0/0), len 100, rcvd 3
*Mar  1 00:07:16.506: IP: s=192.168.100.2 (local), d=192.168.100.1 (FastEthernet0/0), len 100, sending
*Mar  1 00:07:16.506: IP: s=192.168.100.1 (FastEthernet0/0), d=192.168.100.2 (FastEthernet0/0), len 100, rcvd 3
Router-01#
*Mar  1 00:07:16.506: IP: s=192.168.100.2 (local), d=192.168.100.1 (FastEthernet0/0), len 100, sending
*Mar  1 00:07:16.510: IP: s=192.168.100.1 (FastEthernet0/0), d=192.168.100.2 (FastEthernet0/0), len 100, rcvd 3
*Mar  1 00:07:16.510: IP: s=192.168.100.2 (local), d=192.168.100.1 (FastEthernet0/0), len 100, sending
*Mar  1 00:07:16.510: IP: s=192.168.100.1 (FastEthernet0/0), d=192.168.100.2 (FastEthernet0/0), len 100, rcvd 3
Router-01#

--------------------------------------------------------------

When I attempt to ping 8.8.8.8

Router-01#ping 8.8.8.8

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 8.8.8.8, timeout is 2 seconds:

*Mar  1 00:07:38.510: IP: s=192.168.100.2 (local), d=8.8.8.8 (FastEthernet0/0), len 100, sending
*Mar  1 00:07:38.514: IP ARP: creating incomplete entry for IP address: 8.8.8.8 interface FastEthernet0/0
*Mar  1 00:07:38.514: IP ARP: sent req src 192.168.100.2 000a.f493.d2a0,
                 dst 8.8.8.8 0000.0000.0000 FastEthernet0/0
*Mar  1 00:07:38.514: IP: s=192.168.100.2 (local), d=8.8.8.8 (FastEthernet0/0), len 100, encapsulation failed.
*Mar  1 00:07:40.514: IP: s=192.168.100.2 (local), d=8.8.8.8 (FastEthernet0/0), len 100, sending
*Mar  1 00:07:40.514: IP ARP throttled out the ARP Request for 8.8.8.8
*Mar  1 00:07:40.514: IP: s=192.168.100.2 (local), d=8.8.8.8 (FastEthernet0/0), len 100, encapsulation failed.
*Mar  1 00:07:42.513: IP: s=192.168.100.2 (local), d=8.8.8.8 (FastEthernet0/0), len 100, sending
*Mar  1 00:07:42.513: IP ARP: sent req src 192.168.100.2 000a.f493.d2a0,
                 dst 8.8.8.8 0000.0000.0000 FastEthernet0/0
*Mar  1 00:07:42.513: IP: s=192.168.100.2 (local), d=8.8.8.8 (FastEthernet0/0), len 100, encapsulation failed.
*Mar  1 00:07:44.516: IP: s=192.168.100.2 (local), d=8.8.8.8 (FastEthernet0/0), len 100, sending
*Mar  1 00:07:44.516: IP ARP: sent req src 192.168.100.2 000a.f493.d2a0,
                 dst 8.8.8.8 0000.0000.0000 FastEthernet0/0
*Mar  1 00:07:44.516: IP: s=192.168.100.2 (local), d=8.8.8.8 (FastEthernet0/0), len 100, encapsulation failed.
*Mar  1 00:07:46.520: IP: s=192.168.100.2 (local), d=8.8.8.8 (FastEthernet0/0), len 100, sending
*Mar  1 00:07:46.520: IP ARP: sent req src 192.168.100.2 000a.f493.d2a0,
                 dst 8.8.8.8 0000.0000.0000 FastEthernet0/0
*Mar  1 00:07:46.520: IP: s=192.168.100.2 (local), d=8.8.8.8 (FastEthernet0/0), len 100, encapsulation failed.
Success rate is 0 percent (0/5)
Router-01#

[Richard Burts · Accepted solution]

Jake

This is really a pretty simple problem.

First lets identify the basic problem: Your static default route points to Fast0/0. But it does not identify a next hop address. So your router must arp for every remote address. If the provider supported proxy arp then this could work. But pretty clearly the provider does not support proxy arp. To fix this you would need a default route which might look something like this:

ip route 0.0.0.0 0.0.0.0 192.168.100.1

Then lets deal with the error message about encapsulation failed. when we look into the output we can see clearly that the router is sending arp requests for 8.8.8.8. But there are no responses to the arp request. (see my point above about proxy arp or not) So the router creates an "incomplete" arp entry for 8.8.8.8

IP ARP: creating incomplete entry for IP address: 8.8.8.8 interface FastEthernet0/0

Now the router attempts to send a packet to 8.8.8.8. But one essential ingredient for sending an IP packet out an Ethernet interface is the destination MAC address. Since the router has no destination MAC address associated with 8.8.8.8 then the result is encapsulation failed.

Fix the issue with the static default route and the encapsulation failed issue will be solved.

HTH

Rick

[ThVoipJakeT91]

Thank you so much Rick. Your suggestion fixed it straight away. It's a good job there are people like you around. I look forward to playing around with the config now that it's connected to the internet.

Enjoy the rest of the weekend.

Jake Turner

[Richard Burts]

Jake

I am glad that you got it to work and that my suggestion was helpful in finding the solution. Thank you for using the rating system for marking this question as answered - and thanks for the points. It makes the forum more useful when people can read a problem and can know that a solution was achieved. Your marking has contributed to this process.

HTH

Rick