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Configuring IPv6 Rapid Development
• Setting 6rd Tunnel Path MTU
• Enabling reassembly of Fragmented Tunnel Packets.
• Fragmented Tunneled IPv4 packets are reassembled by BR before decapsulation.
service cgn demo
RP/0/RP0/CPU0:BR1#show cgn tunnel v6rd 6rd1 statistics
Incoming fragments count
Reassembled packet count
Reassembled fragments count
ICMP incoming fragments count
Total fragment drop count
Fragments dropped due to timeout
Duplicate fragments drop count
No DB entry fragments drop count
Fragments dropped due to security check failure
Insufficient IPv4 payload fragment drop count
Unsupported protocol fragment drops
Invalid IPv6 prefix fragment drop count
Incoming ICMP fragment count
• ICMP Throttling
• Reset DF bit
• Additional Information:
• "An Anycast Prefix for 6to4 Relay Routers", RFC 3068, June 2001.
• "Security Considerations for 6to4", RFC 3964, December 2004.
Cisco IOS XR Carrier Grade NAT Configuration Guide for the Cisco CRS Router, Release 5.2.x
76
◦ By default the 6rd Tunnel MTU value is 1280.
service cgn demo
service-type tunnel v6rd 6rd1
path-mtu 1480
commit
service-type tunnel v6rd 6rd1
reassembly-enable
commit
◦ By default CGSE throttles 1 per core ( we have 64 cores in CGSE)
RP/0/RP0/CPU0:BR1#config
RP/0/RP0/CPU0:BR1(config)#service cgn cgn1
RP/0/RP0/CPU0:BR1(config-cgn)#protocol icmp rate-limit ?
<0-65472>
ICMP rate limit per second, should be multiple of 64
commit
◦ Tunneled IPv4 packets from BR will have DF bit reset (0) which will allow fragmentation in the
path to RG.
◦ By default it is set to 1 to support Anycast routing
service cgn demo
service-type tunnel v6rd 6rd1
reset-df-bit
commit
◦IPv6 Rapid Deployment on IPv4 Infrastructures (6rd) – http://tools.ietf.org/html/rfc5969
◦ ICMPv4 to ICMPv6 Translation as per http://tools.ietf.org/html/draft-ietf-behave-v6v4-xlate-22
◦ Basic Transition Mechanisms for IPv6 Hosts and Routers", RFC 4213, October 2005.
Implementing Carrier Grade NAT on Cisco IOS XR Software
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OL-32659-01
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