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Forum Replies

  1. Hello Renne,

    What does " 2.0.0.0/24 is subnetted, 1 subnets" mean in below output?


    Branch#show 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, su - IS-IS summary, L1 - IS-IS level-1,
           o - ODR, P - periodic downloaded static route
    
    Gateway of last resort is not set
    
    C    192.168.12.0/24 is directly connected, FastEthernet0/0
         2.0.0.0/24 is subnetted, 1 subnets
    C       2.2.2.0 is directly connected, FastEthernet1/0
  2. Hi Rajagopal,

    2.0.0.0 /8 is a class A network and 2.2.2.0 /24 is a "subnet" of this class A network.

    The routing table will always show the class A network address (2.0.0.0 /8) and the subnets below it (2.2.2.0 /24).

    Hope that helps!

    Rene

  3. Hi Rene

    I set up a simple network PC1 <-> R1 <-> R2 <-> PC2
    All the static routes are implemented, pings work from PC1 to PC2. However when i do a trace from PC2 to PC1 or vice versa, I always get the (ICMP type:3, code:3, Destination port unreachable) at the end of the route hop.

    PC2&gt; trace 192.168.1.1
    trace to 192.168.1.1, 8 hops max, press Ctrl+C to stop
     1   192.168.2.254   10.000 ms  9.000 ms  10.001 ms
     2   192.168.12.1   20.001 ms  20.001 ms  19.001 ms
     3   *192.168.1.1   31.002 ms (ICMP type:3, code:3, Destination port unreachable)

    I know that the trace was successful, but why does it say Destination port unreachable ?

    Thanks,
    Veeral

  4. Hi Rene,

    Another website I was looking at suggested the following:

    ip route 192.168.1.0 255.255.255.0 serial0/2 - Local (outbound) interface can be used ONLY on point-to-point basis.

    ip route 192.168.1.0 255.255.255.0 10.1.1.1 - The next hop router's IP address CAN be used on Point-to-point links but MUST be used on multiaccess links.

    What is meant by this? Is there a hard and fast rule that must be used when deciding to use the router's exiting interface name instead of the next hop address?

    My home router has the gateway of last resort as:

    ip route 0.0.0.0 0.0.0.0 Dialer0

    Could I instead use:

    ip route 0.0.0.0 0.0.0.0 x.x.x.x where x is the ISP's gateway.

    What are the advantages/disadvantages?

    Cheers,

    Matt.

  5. andrew says:

    Florian,
    In the case of a point-to-point link, it is always sufficient to specify the outgoing interface. In the case of a broadcast/multi-access interface (like Ethernet), Cisco's best practice is to specify BOTH the interface AND the next hop IP address. While in most cases, you can get away with using only the next-hop IP, there are a few circumstances where this can result in unexpected behavior. Cisco has a pretty good article explaining how you can get into trouble without specifying both here:

    http://www.cisco.com/c/en/us/support/docs/dial-access/floating-static-route/118263-technote-nexthop-00.html

    The take away from the article is this:

    Conclusion

    Cisco highly recommends that you specify the outbound interface and the next hop IP address when you configure static routes. When the outbound interface is a point-to-point type of link (for example, a serial link), the specification of the next hop address is not needed.

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