[nsp] Cisco IMA -- Throughput

From: Pavane, Brian (brian.pavane@ggn.com)
Date: Sun Sep 24 2000 - 17:37:05 EDT


I have recently setup a link between two Cisco 3640's each with a 4T1 IMA
card. This is a back-to-back setup, with no true ATM switch in the middle,
just 4 T1's from the phone company. This link should be 6mbps, however,
with overhead, I would expect for it to be around 5mbps. The problem is,
that in testing, I am only seeing about 3mbps through this link. I find
that to be unreasonably low. I have included below the configuration and
diagnostics output for these two routers.

There is a line in the 'show atm interface atm 2/0, 2/1, 2/2, 2/3" command
that reports the available bandwidth as 1mbps. This seems odd to me.

Does anyone have any ideas or any experience with Cisco IMA?

Router 1:

interface ATM2/0
 no ip address
 no ip directed-broadcast
 no atm ilmi-keepalive
 ima-group 0
 clock source internal
 no scrambling-payload
 cablelength short 133
!
interface ATM2/1
 no ip address
 no ip directed-broadcast
 no atm ilmi-keepalive
 ima-group 0
 clock source internal
 no scrambling-payload
 cablelength short 133
!
interface ATM2/2
 no ip address
 no ip directed-broadcast
 no atm ilmi-keepalive
 ima-group 0
 clock source internal
 no scrambling-payload
 cablelength short 133
!
interface ATM2/3
 no ip address
 no ip directed-broadcast
 no atm ilmi-keepalive
 ima-group 0
 clock source internal
 no scrambling-payload
 cablelength short 133
!
interface ATM2/IMA0
 ip address 192.168.1.1 255.255.255.252
 no ip directed-broadcast
 no atm ilmi-keepalive
 pvc 0/33
  encapsulation aal5snap
 !
!

3640-1#show atm pvc
            VCD / Peak Avg/Min Burst
Interface Name VPI VCI Type Encaps SC Kbps Kbps Cells
Sts
2/IMA0 1 0 33 PVC SNAP UBR 6000
UP
3640-1#

Cisco-1#show ima interface
Interface ATM2/IMA0 is up
        Group index is 1
        Ne state is operational, failure status is noFailure
        Active links bitmap 0xF
    IMA Group Current Configuration:
        Tx/Rx configured links bitmap 0xF/0xF
        Tx/Rx minimum required links 1/1
        Maximum allowed diff delay is 25ms, Tx frame length 128
        Ne Tx clock mode CTC, configured timing reference link ATM2/0
        Test pattern procedure is disabled
    IMA Group Current Counters (time elapsed 293 seconds):
        0 Ne Failures, 0 Fe Failures, 0 Unavail Secs
    IMA Group Total Counters (last 24 hours):
        0 Ne Failures, 0 Fe Failures, 0 Unavail Secs
    IMA link Information:
        Link Physical Status NearEnd Rx Status Test Status
        ---- --------------- ----------------- -----------
        ATM2/0 up active disabled
        ATM2/1 up active disabled
        ATM2/2 up active disabled
        ATM2/3 up active disabled

Cisco-1#

3640-1#show atm interface atm 2/0
Interface ATM2/0:
AAL enabled: AAL5 , Maximum VCs: 256, Current VCCs: 0

Maximum Transmit Channels: 0
Max. Datagram Size: 4496
PLIM Type: DS1, Framing is T1 ESF, TX clocking: INTERNAL
Cell-payload scrambling: OFF
0 input, 0 output, 0 IN fast, 0 OUT fast, 0 out drop
 Avail bw = 1000 ***** NOTE: ONLY 1mbps? *****
Config. is ACTIVE
Cisco-1#

Router 2:

interface ATM2/0
 no ip address
 no ip directed-broadcast
 no atm ilmi-keepalive
 ima-group 0
 no scrambling-payload
 cablelength short 133
!
interface ATM2/1
 no ip address
 no ip directed-broadcast
 no atm ilmi-keepalive
 ima-group 0
 no scrambling-payload
 cablelength short 133
!
interface ATM2/2
 no ip address
 no ip directed-broadcast
 no atm ilmi-keepalive
 ima-group 0
 no scrambling-payload
 cablelength short 133
!
interface ATM2/3
 no ip address
 no ip directed-broadcast
 no atm ilmi-keepalive
 ima-group 0
 no scrambling-payload
 cablelength short 133
!
interface ATM2/IMA0
 ip address 192.168.1.2 255.255.255.252
 no ip directed-broadcast
 no atm ilmi-keepalive
 pvc 0/33
  encapsulation aal5snap
 !

Brian Pavane



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