Point to Point Links
Terms
P2P — Point-to-Point
A link where the only devices on the network are directly attached to each other.
Ping Pong Attack
A device off-link sends a ping to an address between two routers.
This happens with v4 and v6.
Neither router knows about or has the address, so they forward it back and forth.
Point-to-Point v4
Number with ‘IP Unnumbered’ or use a /31.
Point-to-Point v6
Use a /127.
Config
- Layer 3 structures should go on ports, not SVIs.
- Use ECMP, not link aggregation.
Layer 3
Config that lives on the port can sense and respond to a link failure in 8 msec.
For an SVI to go down, it must be the only port, and it must sense the interface down, this takes 150+ msec.
References
RFC 3021 - Using 31-Bit Prefixes on IPv4 Point-to-Point Links
RFC 6164 - Using 127-Bit IPv6 Prefixes on Inter-Router Links
IPv6 Security Myths and Legends
Enterprise Campus Design - Multilayer Architectures and Design Principles - Cisco Live 2023