Example for RIP: Load Balancing

• If multiple paths exist to a particular destination, RIP will load balance between those paths (by default, up to 4) only if the metric (hop count) is equal

Example for RIP: Load Balancing

R1:

R1(config-if)#router rip
R1(config-router)#network 10.0.0.0
R1(config-router)#network 20.0.0.0
R1(config-router)#network 30.0.0.0

R2:

R2(config-if)#router rip
R2(config-router)#network 20.0.0.0
R2(config-router)#network 40.0.0.0

R3:

R3(config)#router rip
R3(config-router)#network 30.0.0.0
R3(config-router)#network 50.0.0.0

R4:

R4(config-if)#router rip
R4(config-router)#network 40.0.0.0
R4(config-router)#network 50.0.0.0
R4(config-router)#network 60.0.0.0

R1:

R1: IP Route

Here, hop count is 2 (i.e. via 20.0.0.2 and 30.0.0.2), to reach the destination 60.0.0.0.

So if I want to reach PC2 (60.0.0.10) from PC1 (10.0.0.10), RIP will work as a load balance to reach destination 60.0.0.10 in R1. 

Routing Information Protocol (RIP)

Routing Information Protocol (RIP)

• Designed for use on smaller networks
• Dynamic routing protocol
• Oldest distance-vector routing protocols
• RIP uses the Bellman-Ford Distance Vector algorithm to determine the best “path” to a particular destination
• Which employ the “Hop count” as a routing metric to find the best path between the source and the destination network
• Routes with lower hop counts are preferred
• Maximum hop count of 15 hops, any network that is 16 hops away or more is considered unreachable to RIP
• If multiple paths exist to a particular destination, RIP will load balance between those paths (by default, up to 4) only if the metric (hop count) is equal
• RIP sends out periodic routing updates (every 30 seconds)
• RIP sends out the full routing table every periodic update
• RIP routes have an administrative distance of 120.

RIP Versions:

1. Version 1 (RIPv1)

2. Version 2 (RIPv2)

• Unless RIPv2 is manually specified, a Cisco will default to RIPv1 when configuring RIP
• RIPv1 routers will sent only Version 1 packets
• RIPv1 routers will receive both Version 1 and 2 updates
• RIPv2 routers will both send and receive only Version 2 updates

RIP Timers:

1.            Update Timer (default 30 seconds) – Routing table update.

2.            Invalid Timer (default 180 seconds) – Interval of time (in seconds) after which a route is    declared invalid

3.            Hold-down Timer (default 180 seconds)

4.            Flush Timer (default 240 seconds) – After expire route entry deleted form routing table.

Recursive lookup

·         A recursive lookup happens when a second search in the routing table has to be done.

Recursive lookup

R1#show ip route

Codes: C - connected, S - static, I - IGRP, 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, E - EGP

       i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area

       * - candidate default, U - per-user static route, o - ODR

       P - periodic downloaded static route

Gateway of last resort is not set

C    10.0.0.0/8 is directly connected, FastEthernet0/0

C    20.0.0.0/8 is directly connected, Serial2/0

R1#configure terminal

Enter configuration commands, one per line.  End with CNTL/Z.

R1(config)#ip route 30.0.0.0 255.0.0.0 20.0.0.2

R1(config)#ip route 40.0.0.0 255.0.0.0 30.0.0.2

R1(config)#ip route 50.0.0.0 255.0.0.0 40.0.0.2

R1#show ip route

Codes: C - connected, S - static, I - IGRP, 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, E - EGP

       i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area

       * - candidate default, U - per-user static route, o - ODR

       P - periodic downloaded static route

Gateway of last resort is not set

C    10.0.0.0/8 is directly connected, FastEthernet0/0

C    20.0.0.0/8 is directly connected, Serial2/0

S    30.0.0.0/8 [1/0] via 20.0.0.2

S    40.0.0.0/8 [1/0] via 30.0.0.2

S    50.0.0.0/8 [1/0] via 40.0.0.2

·         If I want to reach 50.0.0.0 Network. I need to go via 40.0.0.2. Router once again searches routing table to reach 40.0.0.0 network. So I need to go via 30.0.0.2 to Reach 40.0.0.0 network. Router again searches routing table to reach 30.0.0.0 network. So I need to go via 20.0.0.2 to Reach 30.0.0.0 network. Finally, 50.0.0.0 network will be reached.