From: William Chen (kwchen@netvigator.com)
Date: Wed Jan 07 2004 - 05:47:37 GMT-3
Dear all,
In DocCD, it says: "You can enable forwarding of IP directed broadcasts on an interface where the broadcast becomes a physical broadcast. If such forwarding is enabled, only those protocols configured using the ip forward-protocol global configuration command are forwarded."
However, in the following testing, I found that ICMP packets is also forwarded. Is there a wrong point in DocCD?
R1#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is not set
C 192.168.1.0/24 is directly connected, Serial0/0
i L1 192.168.2.0/24 [115/20] via 192.168.1.2, Serial0/0
R1#sh ip int brief | ex unass
Interface IP-Address OK? Method Status Protocol
Serial0/0 192.168.1.1 YES manual up up
R1#p 192.168.2.255
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.2.255, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 60/71/116 ms
R1#
*Mar 1 06:49:34.054: ICMP: echo reply rcvd, src 192.168.1.2, dst 192.168.1.1
*Mar 1 06:49:34.082: ICMP: echo reply rcvd, src 192.168.2.5, dst 192.168.1.1
*Mar 1 06:49:34.114: ICMP: echo reply rcvd, src 192.168.1.2, dst 192.168.1.1
*Mar 1 06:49:34.142: ICMP: echo reply rcvd, src 192.168.2.5, dst 192.168.1.1
*Mar 1 06:49:34.174: ICMP: echo reply rcvd, src 192.168.1.2, dst 192.168.1.1
*Mar 1 06:49:34.202: ICMP: echo reply rcvd, src 192.168.2.5, dst 192.168.1.1
*Mar 1 06:49:34.234: ICMP: echo reply rcvd, src 192.168.1.2, dst 192.168.1.1
*Mar 1 06:49:34.262: ICMP: echo reply rcvd, src 192.168.2.5, dst 192.168.1.1
*Mar 1 06:49:34.294: ICMP: echo reply rcvd, src 192.168.1.2, dst 192.168.1.1
*Mar 1 06:49:34.322: ICMP: echo reply rcvd, src 192.168.2.5, dst 192.168.1.1
Best Regards,
William Chen
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