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Changes for page IPv6

Last modified by Sebastian Marsching on 2022/05/29 14:06
From version 4.1
edited by Sebastian Marsching
on 2022/05/29 14:06
Change comment: There is no comment for this version
To version 1.2
edited by Sebastian Marsching
on 2022/05/29 13:29
Change comment: Added tag [Network]

Summary

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1 -Network.IP.WebHome
1 +Miscellaneous.Network.IP.WebHome
Content
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23 23  
24 24  With the default MTU setting of 1480 I experienced strange problems: Sometimes, connections got "stuck". By manually setting the MTU for the `tun6to4` interface to 1280 these problems could be solved. I guess, that these problem might be related to packet fragmentation when encapsulating the IPv6 packet within an IPv4 packet.
25 25  
26 -See also: [[Path MTU Discovery issues|doc:Network.IP.WebHome|anchor="HPathMTUDiscoveryIssues"]]
26 +See also: [[Path MTU Discovery issues|doc:Miscellaneous.Network.IP.WebHome|anchor="HPathMTUDiscoveryIssues"]]
27 27  
28 28  # IPv6 with Xen routed setup
29 29  
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89 89  1. Configuration gets easier: We do not have to create host routes, the routes will be automatically determined by the subnet prefix for the address. In the example
90 90  
91 91  above, a route for target `2002:ffff:ffff:1::/64` using the correct `vif`-device will be created automatically. There is also no need to manually configure a host-route to the gateway within the domU: The gateway's address (for `mydomu1` in the example it is `2002:ffff:ffff:1::1`) is within the subnet of the DomU.
92 -
93 93  1. We can easily add extra IP addresses to the DomU: As the Dom0 routes the whole subnet to the DomU, we can just add any address (except the gateway address) within
94 94  
95 95  the `/64` subnet to the DomU, without having to change any configuration within the Dom0.
95 +1. The IPv6 address space is vast: If we have a `/48` subnet for the whole Xen host and we use a `/64` subnet for each DomU, we can create up to nearly 2^16 [DomUs](https://sebastian.marsching.com/wiki/DomUs) on one Xen host. These are more [DomUs](https://sebastian.marsching.com/wiki/DomUs) than you will ever run on a single Xen host.
96 96  
97 -1. The IPv6 address space is vast: If we have a `/48` subnet for the whole Xen host and we use a `/64` subnet for each DomU, we can create up to nearly 2^16 DomUs on one Xen host. These are more DomUs than you will ever run on a single Xen host.
98 -
99 99  In order to make this setup work, we still have to ensure that the script `/etc/xen/scripts/vif-routed-ipv6` is called on the startup of a DomU. The easiest way is to patch `/etc/xen/scripts/vif-routed` using the following patch:
100 100  
101 101  ```diff
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319 319   mkdir -p "`dirname "${prefix_file}"`"
320 320   echo -n "${new_prefix}" >"${prefix_file}"
321 321  fi
320 +
322 322  ```
323 323  
324 324  In this script, you have to adjust your internally used prefix (when choosing a ULA prefix, you should use a random number from the range fc::/7 in order to avoid colissions when connecting different networks using addresses from the ULA space). Like in the other configuration files, you have to change the interface name from `eth0` to whichever is the name of the interface that connects to the Internet router.
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340 340  
341 341  In my case, the actual setup is even a bit more complex: I do not want the internal router to be a single point of failure. For the DSL router on the edge of the network this is acceptable because there is no reasonable way to avoid this. A simple router box is also less likely to fail than a "real" computer and software updates requiring a reboot are less frequent, too.
342 342  
343 -I will not discuss here the details of the fail-over setup of the network interfaces. I use a [[HA solution|doc:Linux.Open_vSwitch.WebHome|anchor="fail-over-interface"]] involving OpenVSwitch. For the rest of this tutorial, it is assumed that fail-over is working for the network interfaces and that the network interface facing the Internet router (`eth0`) uses the same MAC address on all nodes of the HA cluster and is only active on a single node at once.
342 +I will not discuss here the details of the fail-over setup of the network interfaces. I use a [HA solution](https://sebastian.marsching.com/wiki/Linux/OpenVSwitch#Using_Open_vSwitch_for_a_high-availability_.2F_fail-over_interface) involving OpenVSwitch. For the rest of this tutorial, it is assumed that fail-over is working for the network interfaces and that the network interface facing the Internet router (`eth0`) uses the same MAC address on all nodes of the HA cluster and is only active on a single node at once.
344 344  
345 345  The remaining challenge is to ensure that the DHCPv6 client uses the same prefix when fail-over from one node to another one happens. If the prefix changed, existing connections would be interrupted.
346 346