Question Of The Day: 02 May, 2008

Topic: IP Services

Configure r1 to see all possible logs to a server with the IP address of 10.1.1.100.

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Yesterday’s Question

Question Of The Day: 01 May, 2008 

Topic: IOS

r1#show ip arp 10.1.123.100
Protocol  Address          Age (min)  Hardware Addr   Type   Interface
Internet  10.1.123.100            1   0000.5e00.0101  ARPA   FastEthernet0/0

What can we tell about the IP address 10.1.123.100 from this output?

Answer: 10.1.123.100 is a VRRP Virtual IP address in VRRP group 1…or it’s being spoofed .

The MAC address 0000.5e00.0101 signifies that a VRRP virtual MAC address.  The ‘0000.5e00.01′ section signifies a VRRP MAC address.  The last two hexadecimal characters represent a VRRP group number from 1 (01) to 255 (ff).

Configuring VRRP

r2#sh vrrp
FastEthernet0/0 – Group 1 
  State is Master 
  Virtual IP address is 10.1.123.100
  Virtual MAC address is 0000.5e00.0101
  Advertisement interval is 1.000 sec
  Preemption enabled
  Priority is 100
  Master Router is 10.1.123.1 (local), priority is 100
  Master Advertisement interval is 1.000 sec
  Master Down interval is 3.609 sec

As I mentioned, this could also be a spoofed address. 

interface FastEthernet0/0
 description ->r1 f1/0 100.1.11.0/30
 mac-address 0000.5e00.0101
 ip address 100.1.123.100 255.255.255.252