Re: Invalid IP address

From: Kerry Thompson (kerryat_private)
Date: Mon Oct 21 2002 - 19:35:15 PDT

  • Next message: Vern Paxson: "Re: Hiding IP addresses in trace data"

    You seem to be correct, someone on 68.84.8.41 is trying to access various
    other sites. One thing that is confusing in the log entries is the port
    number (0) which is being reported. Cisco access lists log the entry as
    port 0 when you don't explicitly specify the port number in the access
    list, so an ACL like :
    
    access-list 100 deny ip 10.0.0.0 0.255.255.255 any log
    
    will create logs with port 0 as the port, however ACLs like :
    
    access-list 100 deny tcp 10.0.0.0 0.255.255.255 any range 0 65535 log
    access-list 100 deny udp 10.0.0.0 0.255.255.255 any range 0 65535 log
    access-list 100 deny ip 10.0.0.0 0.255.255.255 any log
    
    will log the port numbers and produce a more understandable output - ie.
    you will be able to see which port and know which service the device is
    attempting to connecting to.
    
    
    Kerry
    
    Steven Lee said:
    >
    >
    > I am seeing this on my router syslog after I applied an access list on
    > the  internal interface. Can anyone tell me what this could be? The
    > 68.84.8.41  is a comcast IP that is active on the network; however,
    > someone inside our  network is attempting to use it to go out to other
    > sites? Thanks for your  help.
    >
    > l7.Info	X.X.X.X	38644: .Oct 21 13:40:27: %SEC-6-IPACCESSLOGP: list 101
    > denied tcp 68.84.8.41(0) -> 67.34.160.17(0), 1 packet
    > 2002-10-21 13:35:37	Local7.Info	X.X.X.X	38645: .Oct 21 13:40:28: %
    > SEC-6-IPACCESSLOGP: list 101 denied tcp 68.84.8.41(0) -> 217.121.116.154
    > (0), 1 packet
    [snip]
    
    -- 
    Kerry Thompson, CCNA CISSP
    Information Systems Security Consultant
    http://www.crypt.gen.nz  kerryat_private
    
    
    
    
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