FIND EIGRP Neighbour K Values

In the last post we have seen how we can find the EIGRP neighbour AS number without looking at the router config. We can also find out the remote router's K values in a similar way.

To demonstrate this I will use the existing topology and change the K values on R1. We know that the default K values are K1=K3=1 and K2=K4=K5=0

I will change the values on R1 to K1=K2=K5=1 and K3=K4=0

Find EIGRP Neighbour AS Number

Today we will see how we can find the EIGRP Neighbour AS number without looking at the config of the remote router.

In the topology, I have R1 which is directly connected to R2.

Let's assume that R1 is the third party router which is configured for EIGRP. R2 is in our control and we need to establish EIGRP neighbourship between them.

Both the routers have been configured with basic IP addresses as below

Site To Site VPN between Cisco Routers with Duplicate LAN IP

In the real world If there is a requirement to setup a site to site VPN connection between two different companies, there may be a specific scenario where both the companies are using the same LAN subnets. In this case, we cannot define the ACL with interesting traffic as the source and the destination subnets will be the same!

We will use the existing topology to illustrate the situation. As one can see, both R1 and R2 has a lookpback0 interface with IP 1.1.1.1/24 which represents the LAN subnet. We need to setup a site to site VPN between these two routers.

We will skip the usual steps to configure the ISAKMP & IPSEC parameters as we have covered those in previous posts. Our focus will be on how we can define the interesting traffic. 

Site To Site VPN between Cisco Routers with NAT & GRE

So far we have seen how to implement site to site VPN connection with NAT between Cisco routers. The limitation of this setup is that we cannot run dynamic routing protocol over IPSEC tunnel as IPSEC doesn't support multicast.  i.e. if we add more subnets on both the sites and want them to access via VPN connection, we will have to configure static routes for each of them.

To overcome this issue, we will configure GRE tunnel between both the routers. GRE tunnel will allow unicast, multicast and broadcast traffic between both the routers.

Site To Site VPN between Cisco Routers with NAT

In the last post we have seen how to implement Site to Site VPN between two Cisco router. Generally these routers are directly connected to the Internet and they also provide internet connectivity to the LAN users.

To illustrate this, I have added a Loopback 0 interface on R4 with the IP address 4.4.4.4/24. Let's assume that it is our destination IP in the Internet. 

Site To Site VPN between Cisco Routers

Today we will see how we can configure site-to-site VPN tunnel between two Cisco routers. As shown in the diagram, R1 and R2 represent routers at Site A and Site B respectively. I have configured Loopback 0 on R1 with IP address 1.1.1.1/24 and on R2 with IP address 2.2.2.2/24. Both the loopback represents LAN subnet at each site. The WAN IP of R1 and R2 are 10.1.13.1 and 10.1.25.1 respectively.

The routers R3, R4 and R5 are ISP routers running OSPF between them. Here is the output from each router showing basic configuration.