I've been tracking an attack all day long, and have been frustrated
trying to figure out both what was being attacked, and how. Finally,
I realized it was *not* ICMP, UDP, or TCP.
#sh access-lists 151
Extended IP access list 151
permit icmp any 184.108.40.206 0.255.255.255 (1023 matches)
permit udp any 220.127.116.11 0.255.255.255 (4347 matches)
permit tcp any 18.104.22.168 0.255.255.255 (86444 matches)
deny ip any 22.214.171.124 0.255.255.255 (5547308 matches)
permit ip any any (4450563 matches)
In the above, notice the disparity? So, my question is...
What the hell kind of packet is it if it's not ICMP, UDP, or TCP?
#access-list 123 permit ?
<0-255> An IP protocol number
eigrp Cisco's EIGRP routing protocol
gre Cisco's GRE tunneling
icmp Internet Control Message Protocol
igmp Internet Gateway Message Protocol
igrp Cisco's IGRP routing protocol
ip Any Internet Protocol
ipinip IP in IP tunneling
nos KA9Q NOS compatible IP over IP tunneling
ospf OSPF routing protocol
tcp Transmission Control Protocol
udp User Datagram Protocol
there's lots of protocols other than these... For example, IPv6 is
protocol number 41.
permit ip any any log
! This will definitely tell you what you're seeing.
Could be GRE, IGMP, anything really.. running netflow would probably let
you know real quick