[c-nsp] Multilink PPP (MLPPP) Asymmetrical Throughput Problem NxT1
Rodney Dunn
rodunn at cisco.com
Sat May 26 08:29:49 EDT 2007
I saw this exact problem from a customer a few months ago. What his
turned out to be was some extra latency on one of the T1 links.
I don't remember if it was in one direction or not though.
How about trying the combinations of 2xT1 bundles to see if you
can isolate one T1 as a particular problem?
Capture 'sh ppp mul' on both sides when you are seeing the
problem and not.
Rodney
On Fri, May 25, 2007 at 10:15:52PM -0400, Sean Shepard wrote:
> I'm encountering an odd problem bonding T1 circuits with Multilink PPP
> (Cisco 7206 down to a 2651XM). In this particular case, I've got three (3)
> T-1 lines bonded together and, taking into account overhead, I'm getting
> (via direct Ethernet -> laptop connection - no other traffic):
>
> 4.2 to 4.3 mbps downstream, but .
> Only around 2.0 mbps upstream (tried two different "check my speed" sites).
>
> I was able to initiate multiple large packet repeating pings between the two
> devices and the show interface statistics showed in the neighborhood of 4.0
> mbps in both directions. This put the CPU in the 60 to 70 percent
> utilization range on the remote 2651XM device (with it originating about 50%
> of the pings but not otherwise routing any traffic, Ethernet interface was
> disconnected) 7206 Utilization (handling traffic for numerous locations) was
> well under 10%. No ACLs or Policy-Maps at either end of the links.
>
> Any suggestions or insight on the problem are greatly appreciated. I've not
> observed this kind of difference on various other 2xT1 (3 mbps) connections
> that I've got in place but this is the first 3xT1. Thanks a bunch!
>
>
> HOST END
> Cisco 7206 (non VXR)
>
> interface Multilink2
> description Multilink (ch16-18)
> ip unnumbered Loopback2
> ppp multilink
> no ppp multilink fragmentation
> multilink-group 2
>
> interface Serial3/0:16
> description MLPPP #1
> mtu 1524
> no ip address
> no ip redirects
> encapsulation ppp
> no fair-queue
> no ppp lcp fast-start
> ppp multilink
> multilink-group 2
> !
> interface Serial3/0:17
> description MLPPP #2
> mtu 1524
> no ip address
> no ip redirects
> encapsulation ppp
> no fair-queue
> ppp multilink
> multilink-group 2
> !
> interface Serial3/0:18
> description MLPPP #3
> mtu 1524
> no ip address
> no ip redirects
> encapsulation ppp
> no fair-queue
> ppp multilink
> multilink-group 2
>
>
>
> REMOTE END
> CISCO 2651XM w/WIC-DSU-T1 Cards
> IOS C2600 Version 12.3(6a)
>
> Router> show run (relevant sections)
>
> network-clock-participate slot 1
> no network-clock-participate wic 0
> no aaa new-model
> ip subnet-zero
> ip cef
> !
> !
> !
> interface Multilink1
> description MultiLink PPP 3xT1
> ip address xx.xx.xx.xx xx.xx.xx.xx
> no ip mroute-cache
> load-interval 30
> ppp multilink
> ppp multilink fragment disable
> ppp multilink group 1
> !
> interface FastEthernet0/0
> description LAN Interface
> ip address xx.xx.xx.xx 255.255.255.248
> speed auto
> full-duplex
> no cdp enable
> !
> interface Serial0/0
> description MLPPP T1 1
> mtu 1524
> no ip address
> encapsulation ppp
> load-interval 120
> no fair-queue
> ppp multilink
> ppp multilink group 1
> ppp multilink endpoint none
> !
> interface Serial0/1
> description MLPPP T1 2
> mtu 1524
> no ip address
> encapsulation ppp
> load-interval 120
> no fair-queue
> ppp multilink
> ppp multilink group 1
> ppp multilink endpoint none
> !
> interface Serial1/0
> description MLPPP T1 3
> mtu 1524
> no ip address
> encapsulation ppp
> load-interval 120
> no fair-queue
> ppp multilink
> ppp multilink group 1
> ppp multilink endpoint none
> !
>
>
>
> ROUTER> show interface
>
> Serial0/0 is up, line protocol is up
> Hardware is PQUICC with Fractional T1 CSU/DSU
> Description: MLPPP T1 1
> MTU 1524 bytes, BW 1544 Kbit, DLY 20000 usec,
> reliability 255/255, txload 1/255, rxload 1/255
> Encapsulation PPP, LCP Open, multilink Open, loopback not set
> Last input 00:00:00, output 00:00:01, output hang never
> Last clearing of "show interface" counters 05:13:27
> Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
> Queueing strategy: fifo
> Output queue: 0/40 (size/max)
> 2 minute input rate 0 bits/sec, 0 packets/sec
> 2 minute output rate 0 bits/sec, 0 packets/sec
> 179815 packets input, 246334673 bytes, 0 no buffer
> Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
> 1 input errors, 0 CRC, 1 frame, 0 overrun, 0 ignored, 0 abort
> 175062 packets output, 233229743 bytes, 0 underruns
> 0 output errors, 0 collisions, 2 interface resets
> 0 output buffer failures, 0 output buffers swapped out
> 0 carrier transitions
> DCD=up DSR=up DTR=up RTS=up CTS=up
>
> Serial0/1 is up, line protocol is up
> Hardware is PQUICC with Fractional T1 CSU/DSU
> Description: MLPPP T1 2
> MTU 1524 bytes, BW 1544 Kbit, DLY 20000 usec,
> reliability 255/255, txload 1/255, rxload 1/255
> Encapsulation PPP, LCP Open, multilink Open, loopback not set
> Last input 00:00:04, output 00:00:04, output hang never
> Last clearing of "show interface" counters 05:13:35
> Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
> Queueing strategy: fifo
> Output queue: 0/40 (size/max)
> 2 minute input rate 0 bits/sec, 0 packets/sec
> 2 minute output rate 0 bits/sec, 0 packets/sec
> 179809 packets input, 246361009 bytes, 0 no buffer
> Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
> 2 input errors, 1 CRC, 1 frame, 0 overrun, 0 ignored, 0 abort
> 175057 packets output, 233616175 bytes, 0 underruns
> 0 output errors, 0 collisions, 2 interface resets
> 0 output buffer failures, 0 output buffers swapped out
> 0 carrier transitions
> DCD=up DSR=up DTR=up RTS=up CTS=up
>
> Serial1/0 is up, line protocol is up
> Hardware is DSCC4 with integrated T1 CSU/DSU
> Description: MLPPP T1 3
> MTU 1524 bytes, BW 1544 Kbit, DLY 20000 usec,
> reliability 255/255, txload 1/255, rxload 1/255
> Encapsulation PPP, LCP Open, multilink Open, loopback not set
> Last input 00:00:05, output 00:00:05, output hang never
> Last clearing of "show interface" counters 05:13:40
> Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
> Queueing strategy: fifo
> Output queue: 0/40 (size/max)
> 2 minute input rate 0 bits/sec, 0 packets/sec
> 2 minute output rate 0 bits/sec, 0 packets/sec
> 179807 packets input, 246218180 bytes, 0 no buffer
> Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
> 5 input errors, 0 CRC, 5 frame, 0 overrun, 0 ignored, 0 abort
> 175054 packets output, 233403514 bytes, 0 underruns
> 0 output errors, 0 collisions, 2 interface resets
> 0 output buffer failures, 0 output buffers swapped out
> 0 carrier transitions
> DCD=up DSR=up DTR=up RTS=up CTS=up
>
>
>
>
>
>
>
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