Does ICMP Redirect message is really bad?











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Due to MITM attack, ICMP redirect message should be blocked. However, original purpose of ICMP redirect message is to inform host better router(or gateway).



Then, Is there a speed issue by disabling ICMP redirect message in host? or negligible?










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    up vote
    2
    down vote

    favorite












    Due to MITM attack, ICMP redirect message should be blocked. However, original purpose of ICMP redirect message is to inform host better router(or gateway).



    Then, Is there a speed issue by disabling ICMP redirect message in host? or negligible?










    share|improve this question
























      up vote
      2
      down vote

      favorite









      up vote
      2
      down vote

      favorite











      Due to MITM attack, ICMP redirect message should be blocked. However, original purpose of ICMP redirect message is to inform host better router(or gateway).



      Then, Is there a speed issue by disabling ICMP redirect message in host? or negligible?










      share|improve this question













      Due to MITM attack, ICMP redirect message should be blocked. However, original purpose of ICMP redirect message is to inform host better router(or gateway).



      Then, Is there a speed issue by disabling ICMP redirect message in host? or negligible?







      icmp






      share|improve this question













      share|improve this question











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      share|improve this question










      asked 4 hours ago









      baeharam

      473




      473






















          1 Answer
          1






          active

          oldest

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          up vote
          2
          down vote



          accepted










          ICMP re-directs are most often seen when you have a host or router A in the same subnet with two other routers B & C and connectivity to both. Consider the following network:



             |__192.168.1.0/24__|
          | | |
          |
          | |___192.168.8.0/24__|
          | | | |
          B C
          |____|_____|____|
          | | |
          A


          A will have a route (most likely a default) pointing to B, and B will have a more specific route to a 192.168.8.0/24 pointing to C.



          Without ICMP redirects, all traffic from A to 192.168.8.0/24 will be routed A->B->C



          With ICMP re-direct enabled, B will inform A that C is a better next-hop and subsequent traffic will be routed A->C.



          Obviously B is an extra hop and depending on what kind of box it is, it may introduce extra latency.



          Disabling ICMP-Redirects and redesigning the network to avoid this situation entirely would be the preferred solution eg:



             |__192.168.1.0/24__|
          | | |
          |
          | |___192.168.8.0/24__|
          | | | |
          B-----C
          |____|__________|
          | | |
          A


          (or remove C entirely and hang 192.168.8.0/24 directly off B).






          share|improve this answer





















          • Then, what you mean is that structure of network is more important than ICMP redirect?
            – baeharam
            4 hours ago










          • ICMP redirect indicates that there is sub-optimal routing configured and tries to resolve this - IMO this is a design problem
            – Benjamin Dale
            40 mins ago











          Your Answer








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          1 Answer
          1






          active

          oldest

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          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes








          up vote
          2
          down vote



          accepted










          ICMP re-directs are most often seen when you have a host or router A in the same subnet with two other routers B & C and connectivity to both. Consider the following network:



             |__192.168.1.0/24__|
          | | |
          |
          | |___192.168.8.0/24__|
          | | | |
          B C
          |____|_____|____|
          | | |
          A


          A will have a route (most likely a default) pointing to B, and B will have a more specific route to a 192.168.8.0/24 pointing to C.



          Without ICMP redirects, all traffic from A to 192.168.8.0/24 will be routed A->B->C



          With ICMP re-direct enabled, B will inform A that C is a better next-hop and subsequent traffic will be routed A->C.



          Obviously B is an extra hop and depending on what kind of box it is, it may introduce extra latency.



          Disabling ICMP-Redirects and redesigning the network to avoid this situation entirely would be the preferred solution eg:



             |__192.168.1.0/24__|
          | | |
          |
          | |___192.168.8.0/24__|
          | | | |
          B-----C
          |____|__________|
          | | |
          A


          (or remove C entirely and hang 192.168.8.0/24 directly off B).






          share|improve this answer





















          • Then, what you mean is that structure of network is more important than ICMP redirect?
            – baeharam
            4 hours ago










          • ICMP redirect indicates that there is sub-optimal routing configured and tries to resolve this - IMO this is a design problem
            – Benjamin Dale
            40 mins ago















          up vote
          2
          down vote



          accepted










          ICMP re-directs are most often seen when you have a host or router A in the same subnet with two other routers B & C and connectivity to both. Consider the following network:



             |__192.168.1.0/24__|
          | | |
          |
          | |___192.168.8.0/24__|
          | | | |
          B C
          |____|_____|____|
          | | |
          A


          A will have a route (most likely a default) pointing to B, and B will have a more specific route to a 192.168.8.0/24 pointing to C.



          Without ICMP redirects, all traffic from A to 192.168.8.0/24 will be routed A->B->C



          With ICMP re-direct enabled, B will inform A that C is a better next-hop and subsequent traffic will be routed A->C.



          Obviously B is an extra hop and depending on what kind of box it is, it may introduce extra latency.



          Disabling ICMP-Redirects and redesigning the network to avoid this situation entirely would be the preferred solution eg:



             |__192.168.1.0/24__|
          | | |
          |
          | |___192.168.8.0/24__|
          | | | |
          B-----C
          |____|__________|
          | | |
          A


          (or remove C entirely and hang 192.168.8.0/24 directly off B).






          share|improve this answer





















          • Then, what you mean is that structure of network is more important than ICMP redirect?
            – baeharam
            4 hours ago










          • ICMP redirect indicates that there is sub-optimal routing configured and tries to resolve this - IMO this is a design problem
            – Benjamin Dale
            40 mins ago













          up vote
          2
          down vote



          accepted







          up vote
          2
          down vote



          accepted






          ICMP re-directs are most often seen when you have a host or router A in the same subnet with two other routers B & C and connectivity to both. Consider the following network:



             |__192.168.1.0/24__|
          | | |
          |
          | |___192.168.8.0/24__|
          | | | |
          B C
          |____|_____|____|
          | | |
          A


          A will have a route (most likely a default) pointing to B, and B will have a more specific route to a 192.168.8.0/24 pointing to C.



          Without ICMP redirects, all traffic from A to 192.168.8.0/24 will be routed A->B->C



          With ICMP re-direct enabled, B will inform A that C is a better next-hop and subsequent traffic will be routed A->C.



          Obviously B is an extra hop and depending on what kind of box it is, it may introduce extra latency.



          Disabling ICMP-Redirects and redesigning the network to avoid this situation entirely would be the preferred solution eg:



             |__192.168.1.0/24__|
          | | |
          |
          | |___192.168.8.0/24__|
          | | | |
          B-----C
          |____|__________|
          | | |
          A


          (or remove C entirely and hang 192.168.8.0/24 directly off B).






          share|improve this answer












          ICMP re-directs are most often seen when you have a host or router A in the same subnet with two other routers B & C and connectivity to both. Consider the following network:



             |__192.168.1.0/24__|
          | | |
          |
          | |___192.168.8.0/24__|
          | | | |
          B C
          |____|_____|____|
          | | |
          A


          A will have a route (most likely a default) pointing to B, and B will have a more specific route to a 192.168.8.0/24 pointing to C.



          Without ICMP redirects, all traffic from A to 192.168.8.0/24 will be routed A->B->C



          With ICMP re-direct enabled, B will inform A that C is a better next-hop and subsequent traffic will be routed A->C.



          Obviously B is an extra hop and depending on what kind of box it is, it may introduce extra latency.



          Disabling ICMP-Redirects and redesigning the network to avoid this situation entirely would be the preferred solution eg:



             |__192.168.1.0/24__|
          | | |
          |
          | |___192.168.8.0/24__|
          | | | |
          B-----C
          |____|__________|
          | | |
          A


          (or remove C entirely and hang 192.168.8.0/24 directly off B).







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered 4 hours ago









          Benjamin Dale

          6,1491036




          6,1491036












          • Then, what you mean is that structure of network is more important than ICMP redirect?
            – baeharam
            4 hours ago










          • ICMP redirect indicates that there is sub-optimal routing configured and tries to resolve this - IMO this is a design problem
            – Benjamin Dale
            40 mins ago


















          • Then, what you mean is that structure of network is more important than ICMP redirect?
            – baeharam
            4 hours ago










          • ICMP redirect indicates that there is sub-optimal routing configured and tries to resolve this - IMO this is a design problem
            – Benjamin Dale
            40 mins ago
















          Then, what you mean is that structure of network is more important than ICMP redirect?
          – baeharam
          4 hours ago




          Then, what you mean is that structure of network is more important than ICMP redirect?
          – baeharam
          4 hours ago












          ICMP redirect indicates that there is sub-optimal routing configured and tries to resolve this - IMO this is a design problem
          – Benjamin Dale
          40 mins ago




          ICMP redirect indicates that there is sub-optimal routing configured and tries to resolve this - IMO this is a design problem
          – Benjamin Dale
          40 mins ago


















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