[NV-L] Cisco Router Community String problem

["Evans, Bill" <Bill.Evans@hq.doe.gov>]

Below is the TCPDUMP output for  a sequence of requests to a Cisco router from NetView 7.1.4 on a SuSE 9.3 platform.  I believe it's associated with a QUICKTEST request which fails.  A subsequent DEMANDPOLL works.

First: Can anyone interpret the "bad udp chksum xxxx!" part.  For the initial request it seems to make no difference. Education is needed on my part.  

The device is a Catalyst 6509 with Cisco Internetwork Operating System Software
IOS (tm) s72033_rp Software (s72033_rp-PK9SV-M), Version 12.2(18)SXD2, RELEASE SOFTWARE (fc1)

09:07:53.144652 goshawk.nmic.doe.gov.50681 > CA0016K5.nmic.doe.gov.snmp: [bad udp cksum edf9!] 
        { SNMPv1 C=xxxxxxxx { GetRequest(27) R=776370  system.sysName.0} }  (DF) (ttl 64, id 7228, len 72)
09:07:53.145758 CA0016K5.nmic.doe.gov.snmp > goshawk.nmic.doe.gov.50681:  { SNMPv1 C=xxxxxxxx
        { GetResponse(37) R=776370  system.sysName.0="CA0016K5.n"} }  (ttl 253, id 38056, len 93)
09:07:53.153488 goshawk.nmic.doe.gov.50681 > CA0016K5.nmic.doe.gov.snmp: [bad udp cksum f15f!] 
        { SNMPv1 { GetRequest(27) R=776380  system.sysName.0} }  (DF) (ttl 64, id 7229, len 70)
09:07:55.081250 goshawk.nmic.doe.gov.50681 > CA0016K5.nmic.doe.gov.snmp: [bad udp cksum f15f!] 
        { SNMPv1 { GetRequest(27) R=776380  system.sysName.0} }  (DF) (ttl 64, id 7232, len 70)
09:07:57.147252 goshawk.nmic.doe.gov.50681 > CA0016K5.nmic.doe.gov.snmp: [bad udp cksum f15f!]
         { SNMPv1 { GetRequest(27) R=776380  system.sysName.0} }  (DF) (ttl 64, id 7235, len 70)
09:07:59.469026 goshawk.nmic.doe.gov.50681 > CA0016K5.nmic.doe.gov.snmp: [bad udp cksum cd0a!] 
        { SNMPv1 C=xxxxxxx { GetRequest(27) R=776380  system.sysName.0} }  (DF) (ttl 64, id 7238, len 72)
09:07:59.469945 CA0016K5.nmic.doe.gov.snmp > goshawk.nmic.doe.gov.50681:  { SNMPv1 C=xxxxxxxx
        { GetResponse(37) R=776380  system.sysName.0="CA0016K5.n"} }  (ttl 253, id 38057, len 93)

Second, The underlying problem is periodic failures of the SNMP status poll to this and other Cisco 6509 and 6513 devices running the s72033_rp level software.  Associated with these failures are syslog entries specifying an authentication failure.  The TCPDUMP trace shows no bad community strings sent but it does show records such as these (with bad UDP cksum).  I can't correlate the GetRequest entries without a community string with these authentication failures. 

Any comments from the NetView community would be appreciated.  I'm pushing the network engineers to bang on the Cisco side for what they can offer.

Thanks to the community for past advice and in anticipation of future feedback.

Bill Evans
DOE NetView Support

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