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--- alternate_address [2023/10/25 16:52] – created bent
+++ alternate_address [2025/01/05 16:03] (current) – [Service script] bent
@@ Line 1: / Line 1: @@
-Hi Bent
+====== Alternate address ======
-So here's what I think we'll need to do (syntax may not be quite right!)
+Based on my experiments with [[prefix_delegation|IPv6 prefix delegation and subnetting]] I determined a prefix to delegate to Steve. Steve has asked for a /64 delegation like the one I would get from him. The prefix became 1011, derived in this manner: My LAN (0019) is actually subnet 0 in the first level (/56), subnet 1 in the next level (/60) and subnet 9 in the third level (/64). So the 1011 is subnet 10 (first level), 1 second level and again 1 third level. The initial 10 could also be interpreted as subnet 1 in a /52 allocation and subnet 0 in the /56 allocation giving a total of four possible subnet levels.
-=== a) Steve's end 2a06:4000:8073:1011::/64 ===
+===== Steve's configuration using 2a06:4000:8073:1011::/64 =====
+(basically excerpts from an email)
-i) on my VPN router
+i) on the VPN router
     ip addr add dev br-lan 2a06:4000:8073:1011::2/64
     ip route add default from 2a06:4000:8073:1011::/64 dev tun2 metric 10    ===> for return traffic
-ii) on ictoan
+ii) on Ictoan
     ip addr add br-lan 2a06:4000:8073:1011:202:12:89:12/64
     ip route add default from 2a06:4000:8073:1011::/64 via 2a06:4000:8073:1011::2  ===> for return traffic
-a) on vultrgate
+a) on Vultrgate
     ip route add 2a06:4000:8073:1011::/64 via tun0
     ip route add 2001:44b8:5135:7c07::/64 dev wg0
     Add 2001:44b8:5135:7c07::/64 to Bent's peer "allowed-ips"
-=== b) Bent's end 2001:44b8:5135:7c07::/64 ===
+===== Bent's end 2001:44b8:5135:7c07::/64 =====
-    i) on gate-rpi
-      ip addr add dev br-lan 2001:44b8:5135:7c07::2/64
-      ip route add default from 2001:44b8:5135:7c07::/64 dev tun2  metric 10    ===> for return traffic
-      ip -6 route add 2a06:4000:8073:1011::/64 dev tun2
-    ii) on Spot
-      ip addr add dev br-lan 2001:44b8:5135:7c07::44/64
-      ip route add default from 2001:44b8:5135:7c07::/64 via 2001:44b8:5135:7c07::2 metric 10  ==> return traffic
-IP numbers and device names may not be correct!
-Some firewall additions may be required.....
-Does this all seem right?????
-Steve
+==== gate-rpi ====
+The basic IP commands are:
+      ip addr add dev eth0 2001:44b8:5135:7c07::44/64
+      ip route add default from 2001:44b8:5135:7c07::/64 dev wg0  metric 10    ===> for return traffic
+      ip -6 route add 2a06:4000:8073:1011::/64 dev wg0
+Two of the three commands are easily transferred to Networkd configurations files but the one with 'default from' isn't. The solution chosen was to write a systemd service file for this. The service file is listed further down. Here is the configuration file for eth0:
+  #/etc/systemd/network/eth0.network
+  [Match]
+  Name=eth0
+  [Network]
+  Address=192.168.19.44/24
+  DNS=192.168.19.5
+  IPForward=yes
+  Address=2a06:4000:8073:19::44/64
+  Address=2001:44b8:5135:7c07::44/64
+  IPv6AcceptRA=yes
+and for the tunnel interface (wg0):
+  #/etc/systemd/network/wg0.network
+  [Match]
+  Name=wg0
+  [Network]
+  Address=10.8.3.2/24
+  IPForward=yes
+  [Route]
+  #Gateway=10.8.3.1
+  Destination=2a06:4000:8073:1011::/6
+==== Spot ====
+Similarly the basic IP commands are:
+      ip addr add dev enp2s0 2001:44b8:5135:7c07::5/64
+      ip route add default from 2001:44b8:5135:7c07::/64 via 2001:44b8:5135:7c07::44 metric 10  ==> return traffic
+The 'default from' entry is again handled by a service file.
+Configuration file for enp2s0:
+  [Match]
+  Name=enp2s0
+  [Network]
+  Address=192.168.19.5/24
+  Gateway=192.168.19.254
+  Address=2a06:4000:8073:19::5/64
+  DHCP=no
+  IPv6AcceptRA=yes
+  [Address]
+  Address=2001:44b8:5135:7c07::5/64
+  PreferredLifetime=0
+(the PreferredLifetime=0 is there to prevent usein this address as source address for outgoing connections
+==== Service script ====
+  #/etc/systemd/system/return-route.service
+  [Unit]
+  Description=Return route for IPv6 traffic
+  After=network-online.target
+  [Service]
+  ExecStart=/usr/bin/ip -6 route add default from 2001:44b8:5135:7c07::/64 via 2a06:4000:8073:19::44 dev enp2s0 metric 10
+  ExecStop=/usr/bin/ip -6 route del default from 2001:44b8:5135:7c07::/64 via 2a06:4000:8073:19::44 dev enp2s0 metric 10
+  Type=oneshot
+  RemainAfterExit=yes
+  [Install]
+  WantedBy=multi-user.target
+This is the script from Spot. The one on gate-rpi is identical except for the interface name which is eth0 on gate-rpi. It doesn't have the 'via' part either.