Thursday, March 6, 2014

RIP Broadcast Updates, IP Directed Broadcasts, Broadcast address

Lessons learned:

RIP Update:
The updates themselves depend on what version of RIP is running.

Broadcast
-RIPv1 default
-RIPv2 optional with # ip rip v2-broadcast

Multicast
-RIPv2 default – uses address 224.0.0.9
Unicast
-RIPv1 / RIPv2 optional
-neighbor (address) – enable unicast update (this does not suppress the multicast of broadcast updates)
This means if I want to send updates only to a neighbor, I will have to setup the neighbor statement on both neighbor routers and then configure the passive interface commands.
-passive-interface (interface) – suppress normal broadcast / multicast updates

You can verify the updates with the cmd –
Debug ip rip
Debug ip packet
Debug ip packet detail

RIP Broadcasts:

R3#sh ip interface fastEthernet 0/0
FastEthernet0/0 is up, line protocol is up
  Internet address is 192.168.23.3/24 – this is the directed broadcast the actuall address will look like 192.168.23.255
  Broadcast address is 255.255.255.255  - this is the broadcast address
  Address determined by non-volatile memory
  MTU is 1500 bytes
  Helper address is not set
  Directed broadcast forwarding is disabled  - this is normally disabled,  due to security vulnerabilities
  Multicast reserved groups joined: 224.0.0.9
  Outgoing access list is not set
  Inbound  access list is not set
  Proxy ARP is enabled
  Local Proxy ARP is disabled
  Security level is default
  Split horizon is enabled
  ICMP redirects are always sent
  ICMP unreachables are always sent
  ICMP mask replies are never sent
  IP fast switching is enabled
  IP fast switching on the same interface is disabled
  IP Flow switching is disabled
  IP CEF switching is enabled
  IP CEF Fast switching turbo vector
  IP multicast fast switching is enabled
  IP multicast distributed fast switching is disabled
  IP route-cache flags are Fast, CEF
  Router Discovery is disabled
  IP output packet accounting is disabled
  IP access violation accounting is disabled
  TCP/IP header compression is disabled
  RTP/IP header compression is disabled
  Policy routing is disabled
  Network address translation is disabled
  BGP Policy Mapping is disabled
  WCCP Redirect outbound is disabled
  WCCP Redirect inbound is disabled
  WCCP Redirect exclude is disabled
R3#

Directed broadcast forwarding is disabled  - normally you’d not want to do this, is this is on it means that devices can now deliver broadcasts onto this subnet.

Logs for v1 and v2 updates:
I enabled rip updated for both v1 and v2 on the interface between two routers talking RIP.
interface FastEthernet0/0
 ip address 192.168.23.3 255.255.255.0
 ip rip send version 1 2
 ip rip receive version 1 2

*Mar  1 00:39:53.779: RIP: sending v1 update to 255.255.255.255 via FastEthernet0/0 (192.168.23.3) RIP v1 updates via the 255 broadcast address off FA0/0
*Mar  1 00:39:53.783: RIP: build update entries

*Mar  1 00:39:53.783:   network 10.0.0.0 metric 1

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