https://www.cisco.com/c/en/us/support/docs/csa/cisco-sa-20110928-ipv6mpls.html
Cisco IOS Software IP Version 6 over Multiprotocol Label Switching Vulnerabilities - Cisco
Cisco IOS Software is affected by two vulnerabilities that cause a Cisco IOS device to reload when processing IP version 6 (IPv6) packets over a Multiprotocol...
ip version 6multiprotocol label switchingcisco iossoftware
https://www.cisco.com/c/en/us/tech/ip/ip-version-6-ipv6/index.html
IP Version 6 (IPv6) - Cisco
This page contains information about IP Version 6 (IPv6) technology.
ip version 6ipv6cisco
https://www.rfc-editor.org/rfc/rfc5072.html
RFC 5072: IP Version 6 over PPP
ip version 6rfc5072ppp