Hi Yep sure enough! I knew I should have put the sniffer on the test, but it was late and I wanted to get to bed. Oh well, it was a good learning experience. -- John Hardman CCNP MCSE ""Jason Couch"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > The access list is actually only blocking the icmp packets on the return > path from the "pinged" router or host. The icmp packets sent outbound by > the router sourcing the pings are actually allowed through the outbound > access list. This can be seen by adding the "log" extension to your access > list commands. Then you should see the following message: > > %SEC-6-IPACCESSLOGDP: list 100 denied icmp 192.168.10.50 -> 192.168.10.20 > (0/0), 1 packet > > The key is that you won't see the same log message for the outbound icmp > packets. You can also run "debug ip packet" to see something similar to the > following: > > IP: s=192.168.10.20 (local), d=192.168.10.50 (Ethernet0), len 100, sending > ICMP type=8, code=0 > IP: s=192.168.10.50 (Ethernet0), d=192.168.10.20 , len 100, access denied > ICMP type=0, code=0 > > The outbound packets were sent, but the return packets were "access denied". > Hence you get: > > C2501-R2#ping 192.168.10.50 > > Type escape sequence to abort. > Sending 5, 100-byte ICMP Echoes to 192.168.10.50, timeout is 2 seconds: > ..... > > because the entire ping path consists of both the forwarding AND the return > path. > > HTH, > Jason > > > > ""John Hardman"" wrote in message > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > Hi > > > > I can't believe I am challenging Priscilla! > > > > I just tried what you are talking about, i.e. that the ACL on the router > > does not effect the traffic generated by the router it's self. > > > > I created an extended ACL to block all ICMP traffic and applied it to E0 > as > > both IN and OUT. Before appling the ACL I can ping just fine to any host > on > > the network and any host on the network can ping the router. After Appling > > the ACL I am not able to ping from the router, or to the router. > > > > I am running 11.1 IOS, maybe it would yield different results with a > > different IOS version. What IOS and platform did you see this behavior? > > > > Here's my config. > > > > Windoze PC 192.168.10.50 --- E0 Router2 192.168.10.20 > > RedHat PC 192.168.10.2 > > > > -------------Router config-------------- > > Current configuration: > > ! > > version 11.1 > > service udp-small-servers > > service tcp-small-servers > > ! > > hostname C2501-R2 > > ! > > enable secret 5 XXX > > enable password none > > ! > > ip subnet-zero > > ! > > interface Ethernet0 > > ip address 192.168.10.20 255.255.255.0 > > ip access-group 100 in > > ip access-group 100 out > > no ip mroute-cache > > no ip route-cache > > ! > > interface Serial0 > > ip address 192.168.50.1 255.255.255.252 > > no ip mroute-cache > > encapsulation ppp > > no ip route-cache > > ! > > interface Serial1 > > no ip address > > no ip mroute-cache > > no ip route-cache > > shutdown > > ! > > ip classless > > logging buffered > > access-list 100 deny icmp any any > > access-list 100 permit ip any any > > ! > > line con 0 > > exec-timeout 0 0 > > line aux 0 > > transport input all > > line vty 0 4 > > exec-timeout 0 0 > > password XXXX > > login > > ! > > end > > > > -----------Router Config-------------- > > > > -----------Ping results----------------- > > > > C2501-R2#ping 192.168.10.50 > > > > Type escape sequence to abort. > > Sending 5, 100-byte ICMP Echoes to 192.168.10.50, timeout is 2 seconds: > > ..... > > Success rate is 0 percent (0/5) > > C2501-R2#conf t > > Enter configuration commands, one per line. End with CNTL/Z. > > C2501-R2(config)#int e0 > > C2501-R2(config-if)#no ip access-group 100 in > > C2501-R2(config-if)#no ip access-group 100 out > > C2501-R2(config-if)#^Z > > C2501-R2# > > %SYS-5-CONFIG_I: Configured from console by console > > C2501-R2#ping 192.168.10.50 > > > > Type escape sequence to abort. > > Sending 5, 100-byte ICMP Echoes to 192.168.10.50, timeout is 2 seconds: > > !!!!! > > Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms > > C2501-R2# > > > > Windoze Ping with ACL ---- > > C:\>ping 192.168.10.20 > > > > Pinging 192.168.10.20 with 32 bytes of data: > > > > Reply from 192.168.10.20: Destination net unreachable. > > Reply from 192.168.10.20: Destination net unreachable. > > Reply from 192.168.10.20: Destination net unreachable. > > Reply from 192.168.10.20: Destination net unreachable. > > > > Ping statistics for 192.168.10.20: > > Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), > > Approximate round trip times in milli-seconds: > > Minimum = 0ms, Maximum = 0ms, Average = 0ms > > > > Windoze Ping without ACL ---- > > > > C:\>ping 192.168.10.20 > > > > Pinging 192.168.10.20 with 32 bytes of data: > > > > Reply from 192.168.10.20: bytes=32 time wrote in message > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > I know it's not what you said. What you said was obvious. I guess it > comes > > > about because I said to test with end devices. Router A is acting like > an > > > end device in your example. I should have been more clear. > > > > > > What is not obvious is that ACLs on Router B do not apply to pings to > and > > > from Router B. Every newbie has probably been bitten by that one, > > > especially in simple labs. > > > > > > Priscilla > > > > > > At 09:42 PM 8/26/01, Brad Ellis wrote: > > > >Priscilla, that's not what I said. Here's what I said: > > > > > > > >"...pings sent by one router will not be filtered by another router? " > > > > > > > >Hence my diagram for further explanation: > > > > > > > >Router A -=- Router B -=- Device A > > > >(-=- can be ethernet x-over, serial back-to-back, etc) > > > > > > > >An ACL is applied on Router B's interface (applied inbound) that is > > > >connected to Router A. What I originally said, and continue to say, is > > that > > > >Router B will most certainly block packets (pings or whatever) coming > > from > > > >Router A...and it is irrelevant if Router A is a router or a host > device. > > > >The ACL on Router B doesnt care if the device sending packets is a > router > > or > > > >an end host device! > > > > > > > >If Router B was initiating the ping and Router B had the ACL applied, > > that > > > >would be a different story. > > > > > > > >ttyl, > > > >-Brad Ellis > > > >CCIE#5796 > > > >[EMAIL PROTECTED] > > > >used Cisco: www.optsys.net > > > > > > > >""Priscilla Oppenheimer"" wrote in message > > > >[EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > > > At 08:06 PM 8/26/01, Brad Ellis wrote: > > > > > >Priscilla, > > > > > > > > > > > >Are you saying that pings sent by one router will not be filtered > by > > > >another > > > > > >router? I beg to differ. > > > > > > > > > > Of course not. Pings sent by the router where the ACL is configured > > are > > > >not > > > > > affected by the ACL. Try it. > > > > > > > > > > Priscilla > > > > > > > > > > > > > > > >-Brad > > > > > > > > > > > >""Priscilla Oppenheimer"" wrote in message > > > > > >[EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > > > > > At 06:26 PM 8/26/01, Brad Ellis wrote: > > > > > > > >Sami, > > > > > > > > > > > > > > > >You'll need to give more info than that. The router does not > > care > > > if > > > > > the > > > > > > > >packets are originated from a host or another router. It will > > > filter > > > > > > > >packets based on packet information, ie, source address, > > destination > > > > > > > >address, port #... > > > > > > > > > > > > > > This filtering happens as part of the packet-forwarding process. > > > >Packets > > > > > > > sent by the router (such as pings) may not go through this > > process. > > > >Sorry > > > > > > > that I don't have the details, but I have run into surprising > > results > > > >in > > > > > a > > > > > > > lab environment when testing access lists from a router. You > need > > to > > > >test > > > > > > > them from end hosts. > > > > > > > > > > > > > > I can't believe I'm challenging a CCIE, ;-) but I was afraid > > nobody > > > >else > > > > > > > would, and I think the question bears more research. > > > > > > > > > > > > > > Priscilla > > > > > > > > > > > > > > >Are you saying the router wont filter packets originated from > the > > > >router > > > > > > > >itself? How are your access-lists applied? Inbound or > Outbound? > > > >What > > > > > >are > > > > > > > >you trying to filter? Explain your situation a little better, > > and > > > > > >include > > > > > > > >your access-list if you so desire. > > > > > > > > > > > > > > > >-Brad Ellis > > > > > > > >CCIE#5796 > > > > > > > >[EMAIL PROTECTED] > > > > > > > >used Cisco: www.optsys.net > > > > > > > > > > > > > > > >""sami natour"" wrote in message > > > > > > > >[EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > > > > > > > Hi All , > > > > > > > > > When I made standard access list I discoverd that it > > > > > > > > > prevented packets originated form PC's and host but > > > > > > > > > not packets originated from other routers.Any idea why > > > > > > > > > this will happen. > > > > > > > > > > > > > > > > > > Best Regards , > > > > > > > > > sami , > > > > > > > > > > > > > > > > > > > > > > > > > > > __________________________________________________ > > > > > > > > > Do You Yahoo!? > > > > > > > > > Make international calls for as low as $.04/minute with > Yahoo! > > > > > >Messenger > > > > > > > > > http://phonecard.yahoo.com/ > > > > > > > ________________________ > > > > > > > > > > > > > > Priscilla Oppenheimer > > > > > > > http://www.priscilla.com > > > > > ________________________ > > > > > > > > > > Priscilla Oppenheimer > > > > > http://www.priscilla.com > > > ________________________ > > > > > > Priscilla Oppenheimer > > > http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=17383&t=17383 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
