IPv6 Routing in Linux

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IPv6 Routing in Linux

• Mahendra M
• Mahendra_M_at_infosys.com
• http//symonds.net/mahmk/

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Why Linux
IPv6 Routing in Linux

• Good stable support for IPv6
• Excellent iproute2 architecture

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Traditional Routing
IPv6 Routing in Linux

• Just one table
• Destination How to reach it

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In Linux
IPv6 Routing in Linux

• We can have a set of such tables ( also known as
  classes )
• A class is a complete routing table
• Number limited to 255
• 0 - not specified class

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In Linux ( contd... )
IPv6 Routing in Linux

• Three built-in classes
• RT_CLASS_LOCAL 255 ( local interface addresses,
  broadcasts, NAT addresses )
• RT_CLASS_MAIN 254 ( all normal routes come here
  by default )
• RT_CLASS_DEFAULT 253

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In Linux ( contd... )
IPv6 Routing in Linux

• Each of these classes is applied to the packets
  satisfying certain conditions.
• Conditions are set by means of - ip rule
• Routing tables are defined by - ip route

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Uses
IPv6 Routing in Linux

• Provides flexibility to routing
• Source based routing
• Routing based on TOS

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IPv6 Route Configuration
IPv6 Routing in Linux

• Tools - ip and route
• /sbin/ip 6 route show dev eth0
• 3ffeffff0f101/64 proto kernel metric 256
  mtu 1500 advmss 1440
• fe80/10 proto kernel metric 256
  mtu 1500 advmss 1440
• ff00/8 proto kernel metric 256
  mtu 1500 advmss 1440
• default proto kernel metric 256
  mtu 1500 advmss 1440
• /sbin/route A inet6

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Case 1
IPv6 Routing in Linux

• Adding an IPv6 route through a gateway
• /sbin/route A inet6 add 2000/3 gw
  3ffeffff0f1011

Your machine
IPv6 Router
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Case 2
IPv6 Routing in Linux

• Add an IPv6 route through an interface
• /sbin/route A inet6 add ltnwgt/ltprefixgt dev
  device
• eg
• /sbin/route A inet6 add 2000/3 dev eth0

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Case 3
IPv6 Routing in Linux

• Your machine as the IPv6 gateway
• echo 1 gt /proc/sys/net/ipv6/conf/all/forwarding
• Optionally, you can start radvd daemon to
  support IPv6 autoconfiguration features
• /usr/local/sbin/radvd

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IPv6 Tunneling
IPv6 Routing in Linux

• IPv6 in IPv4 tunneling
• i.e tunneling a v6 address through a v4 address
• ip tunnel add sixbone mode sit remote
  172.22.33.44 local 172.20.30.1 ttl 255
• ip link sixbone up
• ip addr add 3ffe406515a21/96 dev sixbone
• ip route add 3ffe/15 dev sixbone

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Dynamic Routing
IPv6 Routing in Linux

• OSPF BGP
• Routing daemons available
• Mrtd ( http//www.mrtd.net )
• Zebra ( http//www.zebra.org )
• Bird ( http//bird.network.cz )

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Issues
IPv6 Routing in Linux

• Non compliance with RFCs
• Tests conducted ( Linux clocked gt 90 and 100 in
  most cases - robustness, tunneling, ICMPv6)
• Lagged behind in
• Neighbour discovery - 34
• IPv6 MTU discovery - 50
• IPv6 Stateless Address Autoconf - 4

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Thankyou
IPv6 Routing in Linux

• Questions ??