Learn How to Configure Static Route in IPv6

When the traffic traverse from one network to another, the network layer device, e.g., router needs to know about the destination network. It does not matter for the router how it gets the information about that destination, but it should be in the routing table of that router.

We can provide the information about the route to the router, either statically or dynamically. The routing process is almost similar in the IPv4 and IPv6. The routing protocols in IPv6 like RIPng (RIP New Generation), OSPFv3, EIGRP for IPv6, IS-IS for IPv6, MP-BGP4 (Multiprotocol BGP-4) have been redefined with the advance features of the IPv6.

In the small network, we can configure the routes statically on every router. But in the big network or networks, we use dynamic routing protocols which provide the information about the route to the router dynamically. You may want to know--How Does Route Selection Work in Cisco Routers?

The prime objective of the static or dynamic routing is to inform the router about the route or the network which are not connected or directly connected to that router.

Here we will discuss about static route in IPv6.

Enable IPv6 on the Router

When we apply IPv6 address on the interface of a router, that router becomes the member of the FF02::1 (All-IPv6 devices) and this router will be a IPv6 device only and will not be capable of forwarding the ICMPv6 Router Advertisement messages and routing protocols packets.

After applying the command 'IPv6 unicast-routing' on the router, that router will become the member of FF02::2 (All-IPv6 routers). Now this router will be a IPv6-Router having the routing capabilities.

When a router receives a request to transfer the traffic for particular destination network which might be connected or not connected with that router, the router will check its routing table against the destination network.

If that destination network is connected to it, the router will forward the traffic on the interface which is indicating the destination network.

Otherwise if the destination network is not connected to that router, it will check its routing table for the destination network. When it finds that destination network is there in its routing table, it will then find who is the next router pointing that network. Then the router will forward that packet to the next router, and the next router will repeat the same process until they reach to the destination.

An example

A company, e.g., LuminisIndia.com having five routers and IPv6 addresses are configured on all the routers. All the routers used in the company should be able to communicate with each other. For achieving this objective, we are supposed to use only the static routing, no dynamic routing.

We will design the network of LuminisIndia.com in the GNS3. You can also use Packetracer or other network simulation software for this lab. 

The basic configuration difference between the static routing and dynamic routing is that in static routing we need to configure static route for all the destination routes or networks which are not directly connected to that router. But in dynamic routing we need to advertise only the routes or networks, which are directly connected.

For better understanding the concept of IPv6 static routing, we will noted down all the routes which are not directly connected to that specific router.

In this exercise we will get the clear idea of how many IPv6 static routes we need to configure on the specific router and it will also help us in troubleshooting.

From R1 perspective in the current topology, there are four networks which are not directly connected to R1 router. These networks are:

1. 2001:23::/64
2. 2001:34::/64
3. 2001:35::/64
4. 2001:36::/64

On R1 we need to configure four IPv6 static routes, which are not directly connected to R1 router.

R2’s routes which are not directly connected:

1. 2001:34::/64
2. 2001:35::/64
3. 2001:36::/64

On R2, we need to configure three IPv6 static routes.

In the same manner we need to find out which routes are not directly connected to R3, R4, R5, and R6.

R3’s route which is not directly connected:

1. 2001:12::/64

R4’s routes which are not directly connected:

1. 2001:12::/64
2. 2001:23::/64
3. 2001:35::/64
4. 2001:36::/64

R5’s routes which are not directly connected:

1. 2001:12::/64
2. 2001:23::/64
3. 2001:34::/64
4. 2001:36::/64

R6’s routes which are not directly connected:

1. 2001:12::/64
2. 2001:23::/64
3. 2001:34::/64
4. 2001:35::/64

Now we have a clear understanding of which IPv6 static routes need to be configured on the particular router.  We can easily calculate how many IPv6 static routes need to configure on a router and these will be equal to the number of routes which are not directly connected to that router.

IPv6 Address Configuration

Assign the IPv6 address on the specified interface of the router R1 as per the topology and make them 'up', with the commands are given below.

Follow the same procedure for all the routers to assign IPv6 addresses to them and make them ‘up’.
We can verify the assigned IPv6 address on R1.

You may use the same command to verify the assigned IPv6 address on each router.

Use 'IPv6 unicast-routing’ command for dynamic routing and ICMPv6 Neighbor Discovery on router R1.

You must make a point to configure this command on each router.

You also can observe that after applying the command 'IPv6 unicast-routing' on the router, that R1 will become the member of FF02::2 (All-IPv6 routers) and able to send Neighbor Discovery Advertisement packets. 

Configure IPv6 addresses and unicast routing on the router R2.

We can check the status of the interfaces with the command ‘show ipv6 interface brief ‘

Enable IPv6 routing on router R2.

Configure the IPv6 addresses and routing on the rest of the routers.

After the configuration of the IPv6 addresses and routing on each router, they are now ready for the configuration of the static routing.

IPv6 Static Route Configuration

On R1 four routes are not directly connected, we have to configure four IPv6 static routes on R1:

On R2 three routes are not directly connected to it, we have to configure three IPv6 static routes on R2:

Configuration of IPv6 static routes on R3, R4, R5, and on R6 will depend upon how many routes are not directly connected to the router.

On R3 the IPv6 static route configuration will be:

On R4 the IPv6 static routes configuration will be:

On R5 the IPv6 static routes configuration will be:

On R6 the IPv6 static routes configuration will be:

When we configure a static route on the router, it reflects in the routing table. Now we will observe the routing table of each router.

IPv6 Routing Table

When a router forwards the traffic to the destination network, before taking that decision, the router needs to check its routing table for that destination network. If that destination network is present in its routing table, then the router will forward the traffic for that route.

We can check the routing table of each router and observe whether all the routes are present in the routing table or not.

In our topology there are total five networks, we will check whether all these five networks are available in the routing table of each router. In the routing table of each router, we will found three types of networks:

1. Connected, means configured on the interface of that router.
2. Local, means the longest matched route or IP address of the connected route.
3. Static, means the IPv6 static route, which we configured for the routes which are not directly connected to that router.

You should consider the 'Connected' and 'Static' routes only, when you count the routes (five routes) on each router.

IPv6 routing table of R1:

We have four IPv6 static routes and one directly connected route. We can say that all the five routes are available in the routing table of R1.

IPv6 routing table of R2:

In the IPv6 routing table of R2 router there are five routes, three are static routes and two are connected routes.

IPv6 routing table of R3:

In R3 IPv6 routing table, one route is IPv6 static route and four routes are directly connected.

In the same way we can observe the IPv6 routing table of R4, R5, and R6.

IPv6 routing table of R4:

IPv6 routing table of R5:

IPv6 routing table of R6:

On each router all the routes are available and any router can forward the traffic for any network. We can use ping and traceroute command to check the communication between the source and destination.

Verification

We will test the connectivity between the devices, starting from R1 router to R4, R5, R6. We are going to use ‘ping’ and ‘traceroute’ commands for that purpose.

IPv6 address of router R4 is 2001:34::4, which is the destination and the source will be 2001:12::1 which is the IPv6 address on the outgoing interface e0/0 of the router R1. We can observe that R1 can reach to R4 router. This is possible due to the destination route 2001:34::0/64, is available on the each routers which exists between the source and the destination.

Here is the testing output from R1-to-R5 and R1-to-R6.

We can test the connectivity between all the routers. With the help of ICMPv6 or ICMP or Ping, we can test connectivity between the source and destination. And with the traceroute command we can test the connectivity between the source and destination and each router as well, which are coming between the source and the destination.

Although static routing is a wonderful option with many benefits, but as the network grows and number of new routers or network or subnets emerge into the existing network, it increasingly becomes difficult for administrator to manage it. The administrator will require to make the changes every time on all the routers, which is a labor intensive task and error susceptive.

In such scenario, the dynamic routing is a much better option. In dynamic routing the administrator need to advertise the networks which are only directly connected to the particular router.

We may consider the following advices while implementing the IPv6 static route:

• In case of IPv6 static route, we can also configure static route without implementing of 'IPv6 unicast-routing'.
• Configuration of static route in IPv6 is similar to IPv4 static route.
• In situations where we are faced with slow bandwidth link, we obviously do not want to use dynamic routing protocols, because these protocols send packets periodically over the network, thereby eating a portion of the bandwidth. In such situations static routing is warranted.
• When the administrator wants to control the specific route or routes used by the router and which routes should be appearing in the routing table, static routing is a good choice.
• If a company has two Internet connections from 2-different ISPs, and we want to use one connection as a primary and other as a backup link. In the configuration of the static routes for both links, ensure to assign lower administrative distance for the primary link, as compared to the backup link. Now the router will forward the traffic from the primary link, and however if the primary link goes down somehow, then router will use the backup link for forwarding the traffic.

Can we do the load-balancing with static routing in IPv6?

What are various other situations, where do you want to recommend the static routing, w.r.t., IPv6?

Any advice about static routing, you may like to share?

Any caution?

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