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New Member

56K CSU/DSU Keepalives

My Problem:

I have 2500 & 2600 connected over a 56k DDS line, both routers are using the

56/64 CSU/DSU Module. The line drops constantly during the day and we really have no good explanation. Syslogging shows a keepalive mismatch, then the line drops and will comeback up after a minute or so. My question is, is it permissible to turn keepalives off? I really can't find anything to back this up. Are there any consequences in doing this. We have just about ruled out telco problems; they have tested the line numerous times. Any help would be appreciated.

JR

12 REPLIES

Re: 56K CSU/DSU Keepalives

Before making any changes, read this link: http://www.cisco.com/univercd/cc/td/doc/cisintwk/itg_v1/tr1915.htm

You can configure the keepalive interval (under interface, keepalive # or no keepalive), which is the frequency at which the IOS sends messages to itself (Ethernet and Token Ring) or to the other end (serial), to ensure a network interface is alive. Keepalives are like a heartbeat. Debug serial interface will show if you what is happening with the keepalives. If they are missed 3 in a row it will reset the interface. Show interface s0/0 will show how many resets. You can also put the interface into loop to possibly see where the problem is.

Hope it helps.

Steve

Silver

Re: 56K CSU/DSU Keepalives

Make sure your keep alive match on both sides of the circuit. The default is ten seconds. You can see this from the show interface serial x command. I would not recommend turning keepalives off.

Does your line drop or just your line protocol ? If it is your line that is dropping you have other problems besides a keepalive mismatch . If it is only your line protocol then it is most likely the issue.

New Member

Re: 56K CSU/DSU Keepalives

Debug serial does indeed show a keepalive mismatch. Local and remote loopback testing show nothing. I have read the link you attatched many times and still can't isolate the problem. Thanks for the replies.

JR

Silver

Re: 56K CSU/DSU Keepalives

Is this FR ? HDLC ? What kind of leased line is it ? Do you have access to both routers ?

New Member

Re: 56K CSU/DSU Keepalives

56k DDS HDLC. Yes I have access to both routers.

Silver

Re: 56K CSU/DSU Keepalives

when you do a show interface on both router what does the keepalive show ?

see the last line below

sh int e0/0

Ethernet0/0 is up, line protocol is up

Hardware is AmdP2, address is 0004.275b.da60 (bia 0004.275b.da60)

Description:

Internet address is

MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

New Member

Re: 56K CSU/DSU Keepalives

Keepalives on both ends are 10 sec.

Silver

Re: 56K CSU/DSU Keepalives

Is it your line or line protocol that drops ?

Silver

Re: 56K CSU/DSU Keepalives

Is it your line or line protocol that drops ?

Silver

Re: 56K CSU/DSU Keepalives

what is the syslog messages you are getting ?

What do your debugs look like ?

New Member

Re: 56K CSU/DSU Keepalives

If you can make this out. Debug serial.........

Serial0/0: HDLC myseq 8158, mineseen 8158*, yourseen 8153, line up

2002-10-03 14:01:56 Local7.Debug 10.4.1.199 989: 6d13h: Serial0/0: HDLC myseq 8159, mineseen 8159*, yourseen 8154, line up

2002-10-03 14:02:06 Local7.Debug 10.4.1.199 990: 6d13h: Serial0/0: HDLC myseq 8160, mineseen 8160*, yourseen 8155, line up

2002-10-03 14:02:16 Local7.Debug 10.4.1.199 991: 6d13h: Serial0/0: HDLC myseq 8161, mineseen 8161*, yourseen 8156, line up

2002-10-03 14:02:26 Local7.Debug 10.4.1.199 992: 6d13h: Serial0/0: HDLC myseq 8162, mineseen 8162*, yourseen 8157, line up

2002-10-03 14:02:36 Local7.Debug 10.4.1.199 993: 6d13h: Serial0/0: HDLC myseq 8163, mineseen 8162, yourseen 8157, line up

2002-10-03 14:02:44 Local7.Debug 10.4.1.199 994: 6d13h: Serial0/0 - Keepalive time mismatch - should be 10 secs, is 19

2002-10-03 14:02:46 Local7.Debug 10.4.1.199 995: 6d13h: Serial0/0: HDLC myseq 8164, mineseen 8164*, yourseen 8159, line up

2002-10-03 14:02:56 Local7.Debug 10.4.1.199 996: 6d13h: Serial0/0: HDLC myseq 8165, mineseen 8165*, yourseen 8160, line up

2002-10-03 14:03:06 Local7.Debug 10.4.1.199 997: 6d13h: Serial0/0: HDLC myseq 8166, mineseen 8166*, yourseen 8161, line up

2002-10-03 14:03:16 Local7.Debug 10.4.1.199 998: 6d13h: Serial0/0: HDLC myseq 8167, mineseen 8167*, yourseen 8162, line up

2002-10-03 14:03:26 Local7.Debug 10.4.1.199 999: 6d13h: Serial0/0: HDLC myseq 8168, mineseen 8168*, yourseen 8163, line up

2002-10-03 14:03:36 Local7.Debug 10.4.1.199 1000: 6d13h: Serial0/0: HDLC myseq 8169, mineseen 8169*, yourseen 8164, line up

2002-10-03 14:03:46 Local7.Debug 10.4.1.199 1001: 6d13h: Serial0/0: HDLC myseq 8170, mineseen 8170*, yourseen 8165, line up

2002-10-03 14:03:56 Local7.Debug 10.4.1.199 1002: 6d13h: Serial0/0: HDLC myseq 8171, mineseen 8171*, yourseen 8166, line up

2002-10-03 14:03:59 Local7.Debug 10.4.1.199 1003: 6d13h: PowerQUICC(0/0): DCD is down.

2002-10-03 14:03:59 Local7.Debug 10.4.1.199 1004:

2002-10-03 14:03:59 Local7.Debug 10.4.1.199 1005: 6d13h: PowerQUICC(0/0): DCD is up.

2002-10-03 14:03:59 Local7.Debug 10.4.1.199 1006:

2002-10-03 14:03:59 Local7.Debug 10.4.1.199 1007: 6d13h: PowerQUICC(0/0): DCD is down.

2002-10-03 14:03:59 Local7.Debug 10.4.1.199 1008:

2002-10-03 14:03:59 Local7.Debug 10.4.1.199 1009: 6d13h: PowerQUICC(0/0): DCD is up.

2002-10-03 14:03:59 Local7.Debug 10.4.1.199 1010:

2002-10-03 14:03:59 Local7.Debug 10.4.1.199 1011: 6d13h: PowerQUICC(0/0): DCD is down.

2002-10-03 14:03:59 Local7.Debug 10.4.1.199 1012:

2002-10-03 14:03:59 Local7.Debug 10.4.1.199 1013: 6d13h: PowerQUICC(0/0): DCD is up.

2002-10-03 14:03:59 Local7.Debug 10.4.1.199 1014:

2002-10-03 14:03:59 Local7.Debug 10.4.1.199 1015: 6d13h: PowerQUICC(0/0): DCD is down.

2002-10-03 14:03:59 Local7.Debug 10.4.1.199 1016:

2002-10-03 14:03:59 Local7.Debug 10.4.1.199 1017: 6d13h: PowerQUICC(0/0): DCD is up.

2002-10-03 14:03:59 Local7.Debug 10.4.1.199 1018:

2002-10-03 14:03:59 Local7.Debug 10.4.1.199 1019: 6d13h: PowerQUICC(0/0): DCD is down.

2002-10-03 14:03:59 Local7.Debug 10.4.1.199 1020:

2002-10-03 14:03:59 Local7.Debug 10.4.1.199 1021: 6d13h: PowerQUICC(0/0): DCD is up.

Silver

Re: 56K CSU/DSU Keepalives

the myseq is the keep alive you are sending out mineseen is what you are geeting back. Your seen is the keepalive you are sending back to the remote router.

2002-10-03 14:02:26 Local7.Debug 10.4.1.199 992: 6d13h: Serial0/0: HDLC myseq 8162, mineseen 8162*, yourseen 8157, line up

2002-10-03 14:02:36 Local7.Debug 10.4.1.199 993: 6d13h: Serial0/0: HDLC myseq 8163, mineseen 8162, yourseen 8157, line up

2002-10-03 14:02:44 Local7.Debug 10.4.1.199 994: 6d13h: Serial0/0 - Keepalive time mismatch - should be 10 secs, is 19

From the above you can see that you received # 8162 back twice for some reason. It was received back at 19 sec after it was sent out that is why you are getting the keepalive mismatch message.

The real problem you are having is your DCD is dropping. This is most likey an issue with your line provider. Have them test the line extensviely from end to end. Many telcos will just test from the closest test point to your router. Make them test the entire circuit. If you can provide loops from your router or CSU , this will help isolate the point of failure more quickly. If you are using an internal CSU, one command you should add under the interface is 'service-module T1 fdl both' this enables the telco to loop your internal CSU, without this command they will tell you they are testing clean to the demarc but can not loop your equipment .

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