Multilink on 3600 Series not working correctly

[jondoe0069]

After going back and forth with AT&T and having them keep passing the buck, I thought maybe someone might be able to see what is going on with our multilink set up:

We order 4 T1's bonded from AT&T and have confirmed that they have a multilink set up on their end and all 4 T1s connect to the same router on their end. Our multilink configuration is pretty basic and our router is putting traffic out onto each T1 as if it is one interface. Pings and NSLookups work fine, etc., but web pages do not display all the way. It seems that with each T1 I disconnect, more of a web page displays. I tried debug ppp multilink events and fragments and I only see fragments, but no events. From what it looks like, it is utilizing all 4 serial interfaces:

Sending 5, 100-byte ICMP Echos to 12.127.17.71, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 52/54/56 ms
Camelot_Rtr#
1d02h: Se0/0 MLP-FS: I seq C0001E30 size 110
1d02h: Se0/1 MLP-FS: I seq C0001E31 size 110
1d02h: Se1/1 MLP-FS: I seq C0001E32 size 110
1d02h: Se1/0 MLP-FS: I seq C0001E33 size 110
1d02h: Se0/0 MLP-FS: I seq C0001E34 size 110

Here is my config:

version 12.2
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname Camelot_Rtr
!
!
!
!
ip subnet-zero
!
!
ip dhcp excluded-address 192.168.1.1 192.168.1.100
!
ip dhcp pool Camelot
network 192.168.1.0 255.255.255.0
default-router 192.168.1.1
dns-server x.x.x.x x.x.x.x
!
!
!
!
!
!
!
!
!
!
!
!
interface Multilink1
ip address x.x.x.x 255.255.255.248
ip nat outside
no cdp enable
ppp multilink
no ppp multilink fragmentation
multilink-group 1
!
interface FastEthernet0/0
ip address 192.168.1.1 255.255.255.0
ip nat inside
speed 100
full-duplex
!
interface Serial0/0
no ip address
encapsulation ppp
no ip route-cache
no ip mroute-cache
no fair-queue
ppp multilink
multilink-group 1
!
interface FastEthernet0/1
no ip address
shutdown
duplex auto
speed auto
!
interface Serial0/1
no ip address
encapsulation ppp
no ip route-cache
no ip mroute-cache
ppp multilink
multilink-group 1
!
interface FastEthernet1/0
no ip address
shutdown
duplex auto
speed auto
!
interface Serial1/0
no ip address
encapsulation ppp
no ip route-cache
no ip mroute-cache
ppp multilink
multilink-group 1
!
interface FastEthernet1/1
no ip address
shutdown
duplex auto
speed auto
!
interface Serial1/1
no ip address
encapsulation ppp
no ip route-cache
no ip mroute-cache
ppp multilink
multilink-group 1
!
ip nat inside source list 1 interface Multilink1 overload
ip classless
ip route 0.0.0.0 0.0.0.0 Multilink1
ip http server
ip pim bidir-enable
!
access-list 1 permit 192.168.1.0 0.0.0.255
!
call rsvp-sync
!
!
mgcp profile default
!
dial-peer cor custom
!
!
!
!
line con 0
logging synchronous
line aux 0
line vty 0 4
login
!
!
end


Any help will be greatly appreciated! Thanks!!

 

[jondoe0069]

Also, I should note that I have a ton of input errors, crc, and frame on my counters for int 0/1, 1/0, and 1/1 but not 0/0. Each of these counts is in the low thousands for each interface.

 

[mahlad29]

Can you post a sho service module for each serail int

sho service module s0/0

then after that add performance statistics to the end

sho service module x/x perf-stat

-Mike

 

[baddos]

I would say it's a MTU issue. You have disabled fragmentation so check to make sure the T1 serial interfaces have the correct MTU set on them. Have AT&T verify what that should be.

 

[justvistin]

I assume that the input errors on 0/1, 1/0, and 1/1 are incrementing (ie they're not historical) ? You can use the 'clear counters' command on the router and re-check the interfaces after 15 mins or so to verify this.

If the errors are incrementing then this is the issue I'd focus on. If the basic settings have been confirmed with AT&T then you may also wish to consider:

1) swapping the serial feeds in from AT&T to see if the errors follow the transmission or remain on the router port (ie if the serial cable currently feeding 0/0 is disconnected from 0/0 and plugged into 0/1, does 0/1 then start running clean and 0/0 start erroring?)

2) similarly - does swapping the cables linking the ntu(s) to each serial port have any affect?
(eg if you swap the serial cable from the ntu to port 0/0, with the serial cable feeding 0/1 does this make any difference?)

Note: this is different to step 1 - in step one only 'one' end of the serial cable is moved (ie the feed from one T1 is moved to an alternate serial port).

On step 2, the entire serial cable is exchanged. The transmission feeding a particular port remains the same, but the cable between the ntu and a specific serial port is exchanged with another).

This may not resolve the issues, but should at least remove the possibility of the router/hardware being the cause of the issue or the serial cables being at fault

If swapping around the ISP feeds and swapping around the serial cables makes no difference, then this should pretty much put the ball back with AT&T - you've proved the router and associated cabling, suggesting a possible transmission issue.

(I'm assuming that the NTU's are supplied by AT&T here).

 

[jondoe0069]

Thanks for all the responses guys! We've sent our configs to AT&T and it seems as if the problem is on their end. We have a conference call with them later this morning and if the issue is resolved then, I will come back and post the problem/ fix to close out the thread. Thanks again!

 

[jondoe0069]

Everything is working now. AT&T gave us the wrong IP address information. Once we were given the correct addresses, everything began working properly. Thanks for all the help and suggestions!