Contents
How do I use IPv6 tunneling over IPv4?
How to Configure IPv6 Over IPv4 Tunnels
- Add the tunnel source addresses. Then, add the tunnel destination addresses. tsrc IPv4-source-addr tdst IPv4-destination-addr up.
- (Optional) Add a logical interface for the source and destination IPv6 addresses. addif IPv6-source-address IPv6-destination-address up.
Does IPv6 allow fragmentation?
The IPv6 sender may perform fragmentation at source because an IPv6 router cannot perform a fragmentation, so if packet is too large for next hop, router will generate an ICMP packet to let the source know that packet is too large in size.
How is fragmentation done in IPv6?
Fragmentation dissects the IP packet into smaller packets prior to transmission. The receiving host performs fragment reassemble and passes the complete IP packet up the protocol stack. Fragmentation is an IP process, TCP and other layers above IP have no involvement.
What kind of tunneling is used for IPv6?
The manual tunnels refer to RFC 4213 which defines how to encapsulate IPv6 packets in IPv4. GRE is a generic encapsulation type that rides on top of IPv4 and isn’t only for IPv6. It can carry many different protocols and if you ever configured an IPSEC VPN with IGPs running through it you had to use GRE.
Are there any issues with fragmentation in IPv4?
Issues with IPv4 Fragmentation. There are several issues that make IPv4 fragmentation undesirable. There is a small increase in CPU and memory overhead in order to fragment an IPv4 datagram. This holds true for the sender as well as for a router in the path between a sender and a receiver.
How does IPv4 fragmentation and path maximum transmission unit discovery work?
This document describes how IPv4 Fragmentation and Path Maximum Transmission Unit Discovery (PMTUD) work and also discusses some scenarios that involves the behavior of PMTUD when combined with different combinations of IPv4 tunnels.
Is the tunnel interface always GRE in ipv6ip?
By default a tunnel interface is always GRE so by using the tunnel mode ipv6ip command I changed it to a “manual” tunnel per RFC 4213. You can also configure the tunnel interface between the physical interfaces but I like to use loopback interfaces.