Gateway of last resort is not set In Cisco Router

Gateway of last resort is not set In Cisco Router or Switch

You may notice the Line “gateway of last resort is not set” in output when you use the cisco command Show IP Route. This short article will explain that why you are getting this message.

Cisco router gateway of last resort

"Gateway of Last Resort is not set” means that there is no default route for IP packets which have no match with routing table. Gateway of last resort are routes use to avoid your router from dropping packets with unknown networks those are not exist in routing table

Routing table have the list of all known routes. Every time when a router receives a packet, router matches it with routing table entries if it present in routing table then it forward to that path and if route not present in routing table then it is forwarded to default gateway or default route.

How to set Gateway of last resort in router

You can configure or set a default gateway, or route of last resort with following commands:

•  ip default-network    
• ip default-gateway    
• ip route 0.0.0.0 0.0.0.0

ip default-gateway

The ip default-gateway command is used when ip routing is disabled on Cisco-router. Following example defines the default route on router to 172.16.15.4:

ip default-gateway 172.16.15.4

ip default-network

Instead of ip default-gateway command, you can use ip default-network when ip routing is enabled on Cisco-router. When you configure ip default-network the router considers routes to that network for installation as the gateway of last resort on the router. Gateways of last resort selected using the ip default-network command are advertised differently depending on which routing protocol is advertise the default route. For IGRP/EIGRP to propagate the route, the network specified by the ip default-network command must be known to IGRP or EIGRP.

RIP advertises a route to 0.0.0.0 if a gateway of last resort is selected using the ip default-network command.

The default route advertised with the ip default-network command is not propagated by IS-IS and OSPF.

IP Route 0.0.0.0

Creating a static-route to unknown network is another way to set the gateway of last resort on a router. IGRP does not recognize a route advertise with static route command to 0.0.0.0. You are required to use the ip default-network command in case of IGRP. EIGRP advertise a route to network 0.0.0.0, but the static route must beredistributed into the routing protocol.

RIP routers running Cisco IOS 12.0T and later does not advertise the default route where as in earlier version it automatically create a default route 0.0.0.0.

Summary:

Use the ip default-gateway command if the ip routing is disabled on Cisco-router and Use the ip default-network and ip route 0.0.0.0 0.0.0.0 commands to set the gateway of last resort on Cisco routers that have ip routing enabled. The way in which routing-protocols advertise the default route differs for each protocol.

Quick Tip:

For setting network of last resort like use the following command:

ip default-network <IP address of gateway>

Redistribute static route into EIGRP re-distribute Static Lab

Redistribute static route into EIGRP

In an inter-network environment, normally you have a single routing-protocol for ease of controlling your network. But when you are connecting the multiple networks, branch office with each other then there may be the different routing protocol.

Route Redistribution permits routes from one routing-protocol to be advertised in-to another routing-protocol. The routing protocol which receives these redistributed-routes are normally marked the routes as external-routes. External-routes are generally less preferred than locally originated-routes.

You can redistribute routes from one routing protocol to same routing protocol, like two separate OSPF with different process ID’s.

Redistribute static route into EIGRP

Similarly you can redistribute static routes and connected interfaces into a routing protocol as well. This article is about the redistributing the static routes into EIGRP process. For simplicity and clear understanding I have designed a lab in GNS3.

Lab Objectives

We have three routers R1, R2 and R3. R1 and R3 are running with EIGRP and our objective is to redistribute the static routes from R2 into EIGRP so that these can be available at R3 as external routes.

I have configured this lab on GNS3 with following configurations:

Configurations on R2

R2(config)#interface f0/0

R2(config-if)#ip address 50.0.0.1 255.255.255.0

R2(config-if)#no shut

R2(config-if)#exit

R2(config)#interface loopback 1

R2(config-if)#ip address 10.10.10.1 255.255.255.0

R2(config-if)#interface loopback 2

R2(config-if)#ip address 20.10.10.1 255.255.255.0

R2(config-if)#interface loopback 3

R2(config-if)#ip address 30.10.10.1 255.255.255.0

R2(config-if)#interface loopback 4

R2(config-if)#ip address 40.10.10.1 255.255.255.0

Configuration of static routes for not directly connected routes:

For static route configurations you are required to advertise destination network with next hop address via static route command as following:

R2(config)#ip route 150.0.0.0 255.255.255.0 50.0.0.2

R2(config)#ip route 100.10.10.0 255.255.255.0 50.0.0.2

R2(config)#ip route 200.10.10.0 255.255.255.0 50.0.0.2

Configurations on R3

R3(config)#int f0/0

R3(config-if)#ip address 150.0.0.2 255.255.255.0

R3(config-if)#no shut

R3(config)#int loopback 1

R3(config-if)#ip address 100.10.10.1 255.255.255.0

R3(config-if)#exit

R3(config)#int loopback 2

R3(config-if)#ip address 200.10.10.1 255.255.255.0

R3(config-if)#exit

R3(config)#router eigrp 10

R3(config-router)#network 150.0.0.0 0.0.0.255

R3(config-router)#network 100.10.10.0 0.0.0.255

R3(config-router)#network 200.10.10.0 0.0.0.255

Configurations on R1

R1(config)#int f1/0

R1(config-if)#ip address 50.0.0.2 255.255.255.0

R1(config-if)#no shutdown

R1(config)#interface fastEthernet 0/0

R1(config-if)#ip address 150.0.0.1 255.255.255.0

R1(config)#router eigrp 10

R1(config-router)#network 150.0.0.0 0.0.0.255

R1(config-router)#network 50.0.0.0 0.0.0.255

R1(config)#ip route 10.10.10.0 255.255.255.0 50.0.0.1

R1(config)#ip route 20.10.10.0 255.255.255.0 50.0.0.1

R1(config)#ip route 30.10.10.0 255.255.255.0 50.0.0.1

R1(config)#ip route 40.10.10.0 255.255.255.0 50.0.0.1

Static Routes redistribution into EIGRP Configurations

For Static Routes redistribution into EIGRP you need to permit all the static routes with a route map which you want to redistribute into EIGRP. For this you are required a access-list with all IP which are going to redistribute in EIGRP.

R1(config)#access-list 7 permit 10.10.10.1

R1(config)#access-list 7 permit 20.10.10.1

R1(config)#access-list 7 permit 30.10.10.1

R1(config)#access-list 7 permit 40.10.10.1

R1(config)#route-map static-to-eigrp permit 10

R1(config-route-map)#match ip address 7

Redistribution Commands:

R1(config)#router eigrp 10

R1(config-route-map)# R1(config-router)#redistribute static route map static-to-eigrp

R1(config-route-map)# R1(config-router)#redistribute static metric 10000 1 255 1 1500 (not compulsory in case of static routes)

Testing and verification of configurations:

After the successful configurations you will find the static routes in R3’s routing table as the external routes:

Network 10.10.10.0, 20.10.10.0, 30.10.10.0 and 40.10.10.0 are the interfaces configured at R1 and after complete configuration you can find these routes in R3 routing table.

You can also perform an end to end ping for testing. Following are some other redistribution labs you can visit these as reference and learning.

• Route redistribution RIP into OSPF And OSPF into RIP
• EIGRP Redistribution of Different AS
• EIGRP OSPF Redistribution