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7.2 Basic 6rd Configuration
To configure 6rd, the user must configure the softwire rule. A sample softwire rule looks like the following:
[edit services]
user@router# show softwire
softwire-concentrator {
v6rd v6rd-dom1 {
}
}
rule v6rd-dom1-r1 {
match-direction input;
term t1 {
}
}
first, a softwire concentrator of type 6rd must be created with its associated IPv4 address. The softwire concentrator
IPv4 address need not be the same as the ingress media interface. In fact, the softwire concentrator and the ingress
media interface don't need to be on the same network. The softwire concentrator is anchored on an IPv4 address
independent of any interface and on a different prefix. The softwire concentrator object also has 6rd domain's
IPv6 prefix and IPv4 prefix of the CE WAN network. The mtu-v4 attribute sets the maximum transmission unit
when encapsulating IPv6 packets into IPv4. In general, v6-in-v4 tunneling reduces the maximum transmission unit
(MTU) of an IPv6 interface by 20 octets, that is if the basic IPv4 encap header does not contain optional fields. The
administrator must configure the IPv6 interface MTU by taking the IPv4 MTU into account and subtracting at least
20 from that to allow room for the IPv4 header. As the services NPU doesn't detect which egress interface the packet
goes out on, the administrator must configure the IPv4 MTU under the softwire concentrator hierarchy by looking at the
routing information. If, after adding the IPv4 header, the packet size grows beyond the IPv4 MTU configured, then the
packet is dropped by the services NPU. This knob is mandatory since it depends on other network parameters under
the administrator control.
Once a softwire concentrator is created, a softwire rule must be created to use it. The aforementioned rule basically
states that any traffic destined to the softwire concentrator address of v6rd-dom1 results in the creation of a new
softwire, if none exists already.
Once a softwire rule is created, it must be used in the service set as in the following:
service-set v6rd-dom1-service-set {
...
...
softwire-rules v6rd-dom1-r1
interface-service {
}
}
Copyright © 2011, Juniper Networks, Inc.
softwire-address 30.30.30.1;
ipv4-prefix 10.10.10.0/24;
v6rd-prefix 3040::0/16;
mtu-v4 1492;
then {
v6rd v6rd-dom1;
}
service-interface sp-3/0/0;
IMPLEMENTATION GUIDE - 6rd Configuration Guide
7
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