PPP is a Layer2 protocol which provides a standard method for transporting multi protocol over Point to point link. It comprises of LCP and NCP sub layers.
LCP – Establishing, Configuring and testing the link.
NCP – Establish and configure different network layer protocol (Layer3)
Simple PPP Configuration:
Simple PPP Configuration involves enabling the PPP encapsulation on the interface and configuring respective IP address on either side. It can be noted that, a /32 entry of peer’s IP address will be installed in routing table as directly connected interface. This /32 entry is mandatory when the setup is dialup with ip address of the PPP interface configured as “ip unnumbered loopback
In the below mentioned example, R1 is configured with 126.96.36.199/24 address which will be installed in R3’s routing table as directly connected interface.
The default behavior of installing the /32 address can be disabled as below,
In dialup kind of setup, we can have the client negotiate and obtain the IP address from server as part of LCP negotiation (IPCP). It can be done in 3 ways as below,
- Local Pool
- Static address
Address negotiation using Local Pool:
Address negotiation using static address:
Routing over PPP negotiated link:
RIP on receiving an update packet, by default will validate the source and check if it is from same subnet. If not, the update packet will be ignored with “RIP: ignored v2 packet from 188.8.131.52 (sourced from one of our addresses)” error message.
This issue can be solved by disabling the source validation in RIP protocol as below,
AFAIK, OSPF is not supported on link with /32 subnet mask. OSPF on receiving hello packet from a neighbor will check Area, Subnet Mask, Hello Interval, Dead Interval, Authentication, Options. If the subnet mask is different from the one received in hello packet, the packet will ignored and there is no way to disable the check.
No Special configuration is required with EIGRP
iBGP doesn’t require any special configuration.
When configuring eBGP, the client with /32 subnet mask will assume the neighbor is not directly connected and will require “neighbor