how block large icmp packets?

how block large icmp packets?

Post by Matt » Thu, 27 Jun 2002 10:18:30



How can I block ICMP fragment packets / Large ICMP packets with pmfirewall
script?
 
 
 

how block large icmp packets?

Post by Av » Thu, 27 Jun 2002 19:59:44



> How can I block ICMP fragment packets / Large ICMP packets with pmfirewall
> script?

#
#-----INCOMING-------
#
#echo reply (pong)
$IPCHAINS -A input  -p icmp --icmp-type  0 -j ACCEPT
#destination unreachable
$IPCHAINS -A input  -p icmp --icmp-type  3 -j ACCEPT
#source quench
$IPCHAINS -A input  -p icmp --icmp-type  4 -j ACCEPT
#time to live (TTL) for traceroute
$IPCHAINS -A input  -p icmp --icmp-type 11 -j ACCEPT
#now deny all other INCOMING icmp packets
$IPCHAINS -A input  -p icmp -j DENY -l
#
#-----OUTGOING------
#
#destination unreachable
$IPCHAINS -A output -p icmp --icmp-type  3 -j ACCEPT
#source quench
$IPCHAINS -A output -p icmp --icmp-type  4 -j ACCEPT
#echo request (ping)
$IPCHAINS -A output -p icmp --icmp-type  8 -j ACCEPT
#now deny all other OUTGOING icmp packets
$IPCHAINS -A output -p icmp -j DENY -l

for detailed info STW....

 
 
 

1. Blocking of ICMP echo packets

Dear All,

For some time now I've had my linux box firewall blocking incoming ICMP
type 8 (echo or ping) packets. Recently we had a problem where a number
of machines on another network were receiving destination unreachable
messages from our ISP's router. What I'm asking (in a very long-winded
way) is whether my blocking ICMP echo packets could in some way have
caused this problem?

Thanks in advance,

Kiril Dunn

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