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nixos/home: Correct river wan-vlan-outer MTU to 1512
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The outer WAN VLAN carries the inner VLAN's frames, whose 4B 802.1Q tag
counts as payload at this layer. To fit the inner's 1508B baby-jumbo
payload plus that tag it needs 1512, not 1508. Harmless before only
because the physical `lan` (9000) absorbed the extra bytes; this makes
the outer's MTU literally reflect what it transports.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Jack O'Sullivan
2026-07-20 10:57:13 +01:00
parent d33f32ce5b
commit 300103f2ba
1 changed files with 3 additions and 2 deletions
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nixos/boxes/home/palace/vms/river.nix
+3 -2
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@@ -174,8 +174,9 @@
matchConfig.Name = "wan-vlan-outer"; matchConfig.Name = "wan-vlan-outer";
vlan = [ "wan-vlan-inner" ]; vlan = [ "wan-vlan-inner" ];
networkConfig = networkd.noL3; networkConfig = networkd.noL3;
# baby jumbo: 1508 so the inner VLAN below can also carry it # baby jumbo: carries the inner VLAN's frames, whose 4B tag counts as payload
linkConfig.MTUBytes = "1508"; # at this layer, so it needs 1512 (inner's 1508B payload + the inner 802.1Q tag)
linkConfig.MTUBytes = "1512";
}; };
# pppd attaches PPPoE to this; just needs to be up with no L3 # pppd attaches PPPoE to this; just needs to be up with no L3
"71-wan-vlan-inner" = { "71-wan-vlan-inner" = {