Cisco Notepad

This is a less well-known First Hop Redundancy protocol, as compared to HSRP, VRRP, and GLBP. It is based on ICMP.

SW2# 

interface Vlan58
 ip address 155.1.58.8 255.255.255.0
 ip irdp
 ip irdp maxadvertinterval 20
 ip irdp minadvertinterval 10
 ip irdp address 155.1.58.8 200

Rack1R5#
!
interface Ethernet0/0
 ip address 155.1.58.5 255.255.255.0
 ip irdp
 ip irdp maxadvertinterval 20
 ip irdp minadvertinterval 10
 ip irdp address 155.1.58.5 100

Rack1R5#sh ip irdp e0/0
Ethernet0/0 has router discovery enabled

Advertisements will occur between every 10 and 20 seconds.
Advertisements are sent with broadcasts.
Advertisements are valid for 60 seconds.
Default preference will be 0.
Proxy for 155.1.58.5 with preference 100.

Rack1SW2#sh ip irdp vlan58
Vlan58 has router discovery enabled

Advertisements will occur between every 10 and 20 seconds.
Advertisements are sent with broadcasts.
Advertisements are valid for 60 seconds.
Default preference will be 0.
Proxy for 155.1.58.8 with preference 200.

Disable SW1 routing, to simulate a host.

Rack1SW1(config)#no ip routing
Rack1SW1(config)#ip ?
 gdp                   Router discovery mechanism

Rack1SW1(config)#ip gdp ?
  eigrp  Discover routers transmitting EIGRP router updates
  irdp   Discover routers transmitting IRDP router updates
  rip    Discover routers transmitting RIP router updates

Rack1SW1(config)#ip gdp irdp

Rack1SW1#sh ip route  
Gateway         Using  Interval  Priority   Interface
155.1.58.8      IRDP       14       200     Vlan58
155.1.58.5      IRDP       14       100     Vlan58

Default gateway is 155.1.58.8

Host               Gateway           Last Use    Total Uses  Interface
ICMP redirect cache is empty

Rack1SW1#trace 155.1.10.10

Type escape sequence to abort.
Tracing the route to 155.1.10.10

  1 155.1.58.8 8 msec 0 msec 0 msec
  2 155.1.108.10 0 msec *  0 msec

Rack1SW1#trace 155.1.45.4

Type escape sequence to abort.
Tracing the route to 155.1.45.4

  1 155.1.58.8 0 msec 8 msec 0 msec
  2  *
    155.1.45.4 1015 msec *
Rack1SW1#trace 155.1.45.4

Type escape sequence to abort.
Tracing the route to 155.1.45.4

  1 155.1.58.5 8 msec 0 msec 9 msec
  2 155.1.45.4 17 msec *  8 msec

Rack1SW1#trace 155.1.0.5

Type escape sequence to abort.
Tracing the route to 155.1.0.5

  1 155.1.58.8 0 msec 8 msec 0 msec
  2 155.1.58.5 0 msec *  0 msec
Rack1SW1#trace 155.1.0.5

Type escape sequence to abort.
Tracing the route to 155.1.0.5

  1 155.1.58.5 8 msec *  0 msec