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Access List question

john.wright
Level 3
Level 3

When one applies an Access-list to an out interface of the ethernet connection to the LAN on a router does that cover the traffic going out to the LAN or the traffic going out of the LAN to the router?

2 Accepted Solutions

Accepted Solutions

Reza Sharifi
Hall of Fame
Hall of Fame

John,

Here are some definitions:

When you refer to a router, these terms have these meanings.

  • Out—Traffic that has already been through the router and leaves the interface. The source is where it has been, on the other side of the router, and the destination is where it goes.

  • In—Traffic that arrives on the interface and then goes through the router. The source is where it has been and the destination is where it goes, on the other side of the router.

  • Inbound —If the access list is inbound, when the router receives a packet, the Cisco IOS software checks the criteria statements of the access list for a match. If the packet is permitted, the software continues to process the packet. If the packet is denied, the software discards the packet.

  • Outbound—If the access list is outbound, after the software receives and routes a packet to the outbound interface, the software checks the criteria statements of the access list for a match. If the packet is permitted, the software transmits the packet. If the packet is denied, the software discards the packet.

More info:

http://www.cisco.com/en/US/products/sw/secursw/ps1018/products_tech_note09186a00800a5b9a.shtml#sourcedefine

HTH

Reza

    View solution in original post

    Ganesh Hariharan
    VIP Alumni
    VIP Alumni
    When one applies an
    Access-list to an out interface of the ethernet connection to the LAN
    on a router does that cover the traffic going out to the LAN or the
    traffic going out of the LAN to the router?

    Hi,

    An access-list applied outbound to  interface filters traffic going TO machines on that interface or segment.

    An access-list applied inbound to interface filters traffic coming FROM machines on that interface or segment.

    Hope to Help !!

    Ganesh.H

    Remember to rate the helpful post

    View solution in original post

    3 Replies 3

    Reza Sharifi
    Hall of Fame
    Hall of Fame

    John,

    Here are some definitions:

    When you refer to a router, these terms have these meanings.

    • Out—Traffic that has already been through the router and leaves the interface. The source is where it has been, on the other side of the router, and the destination is where it goes.

    • In—Traffic that arrives on the interface and then goes through the router. The source is where it has been and the destination is where it goes, on the other side of the router.

    • Inbound —If the access list is inbound, when the router receives a packet, the Cisco IOS software checks the criteria statements of the access list for a match. If the packet is permitted, the software continues to process the packet. If the packet is denied, the software discards the packet.

    • Outbound—If the access list is outbound, after the software receives and routes a packet to the outbound interface, the software checks the criteria statements of the access list for a match. If the packet is permitted, the software transmits the packet. If the packet is denied, the software discards the packet.

    More info:

    http://www.cisco.com/en/US/products/sw/secursw/ps1018/products_tech_note09186a00800a5b9a.shtml#sourcedefine

    HTH

    Reza

      Ganesh Hariharan
      VIP Alumni
      VIP Alumni
      When one applies an
      Access-list to an out interface of the ethernet connection to the LAN
      on a router does that cover the traffic going out to the LAN or the
      traffic going out of the LAN to the router?

      Hi,

      An access-list applied outbound to  interface filters traffic going TO machines on that interface or segment.

      An access-list applied inbound to interface filters traffic coming FROM machines on that interface or segment.

      Hope to Help !!

      Ganesh.H

      Remember to rate the helpful post

      john.wright
      Level 3
      Level 3

      Thanks for the reply. It was very helpful.

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