3 Bonded T1s setup point to point on two 2811s

Unanswered Question
Sep 28th, 2010

Good Morning,

     I am currently trying to configure two 2811 routers with 3 HWIC-1DSU-T1 cards each to bond three T1s and bridge or LAN to a remote location.  I work for a power company and the T1's are ours provided by our Telco department.  For setup and testing however I have both the routers in my office connected with T1 crossover cables.  Below are my configurations, I am new to cisco routers so be gentle.  I want the local end to be ip address and the remote end to be  Our default gateway for the network is  I would also like to keep everything on one subnet if possible.  With the attached configs I cant even ping between the routers...what am I doing wrong?  Also, can anyone recommend any self-study courses for the cisco 2800 series stuff?  Thanks in advance!

Below is a "sh int serial 0/0/0"

Serial0/0/0 is up, line protocol is up
  Hardware is GT96K with integrated T1 CSU/DSU
  MTU 1500 bytes, BW 1544 Kbit/sec, DLY 20000 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation PPP, LCP Open, multilink Open
  Link is a member of Multilink bundle Multilink1, loopback not set
  Keepalive set (10 sec)
  Last input 00:00:16, output 00:00:00, output hang never
  Last clearing of "show interface" counters 16:47:22
  Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 23
  Queueing strategy: weighted fair  [suspended, using FIFO]
  FIFO output queue 0/40, 23 drops
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     387635 packets input, 36565847 bytes, 0 no buffer
     Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
     330629 packets output, 22906294 bytes, 0 underruns
     0 output errors, 0 collisions, 1886 interface resets
     0 unknown protocol drops
     0 output buffer failures, 0 output buffers swapped out
     4 carrier transitions
     DCD=up  DSR=up  DTR=up  RTS=up  CTS=up

I have this problem too.
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Calin Chiorean Tue, 09/28/2010 - 06:13


I have applied your configuration to a back-to-back setup of 2 Cisco routers and it seems to work for me. Did you check your interfaces? Everything is up and running there? If you do a "show bridge" on both routers, do you see anything in the output? From one router, can you ping your own BVI IP?

If you have a back-to-back scenario in a lab environment, forget about the default gateway ( as it should work without it.



jnbinkley0 Tue, 09/28/2010 - 10:03

Hi Calin,

     Thanks for you reply.  After reading your reply I just left the routers to run while I took care of some other stuff.  When i came back I noticed I was pinging both routers and through the routers to a computer I have behind him.  Whats odd is it works when no traffic is passing over them but as soon as start to load a web page or something like that everything drops off and I can ping everything very intermittenly.  I can run wireshark on the computer that is on the remote end of the bridge and it shows tons and tons or ARP requests....Any ideas?



Calin Chiorean Wed, 09/29/2010 - 00:59

You have a L2 / L3 issue there, but due to the fact that there are so less details here, it's quite hard for me to understand what you want to achieve.

Right now, you have 2 routers connected back-to-back and bridged over 3 x T1 multilink ppp, but what's next? where is your webserver located and from where are you trying to access it?



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