how to communicate 1 way?

[abellanosachristian]

my title may be confusing because I don't even know what it is called by i will try my best to explain the scenario.

I have Two PCs. Between them may be routers and switches. I want PCA to ping PCB successfully but PCB can't ping PCA. How am I able to do this?

[mdiciero1]

Use access lists

http://www.cisco.com/c/en/us/support/docs/security/ios-firewall/23602-confaccesslists.html

[abellanosachristian]

I have tried ACL but they cause all PCs not to ping each other. 

[John Blakley]

You'll need to use reflexive acls for this. PCA will be allowed out, but PCB will not be allowed in unless a session was started from PCA (reply traffic). Take a look here:

http://packetlife.net/blog/2008/nov/25/reflexive-access-lists/

You should also be able to use CBAC as well...

HTH,

John

** Please rate all helpful posts **

[abellanosachristian]

I may be a total noob but i don't find reflect as an option on permit ip any any. the following are the only options i could use, dscp and precedence.

I am using packet tracer 6.2 and I also tried different routers.

[John Blakley]

I'm not sure about packet tracer. Basically, you create 2 ACLs:

ip access-list ext Outside_In 

evaluate Outside_Usage

deny ip any any

ip access-list ext Inside_Out

permit ip any any reflect Outside_Usage

int fa0/0 (Outside Interface)

ip access-group Inside_Out out

ip access-group Outside_In in

HTH,

John

[abellanosachristian]

I tried to do that but whenever i enter "evaluate Outside_Usage" it says invalid input detected right at evaluate. Basically my router on packet tracer doesnt have evaluate command nor reflect.

[Jon Marshall · Accepted solution]

The suggestion was to use an acl that only allowed ICMP echo-reply from PC B to PC A and then apply that to the L3 interface acting as the default gateway for PCB.

Jon

[abellanosachristian]

im not able to read your reply here but i can read it on my gmail. Nonetheless, you answer was spot on thank you very much you helped me alot.