Minecraft Forums

This just started today for all my servers (1.8.9 vanilla, 1.8.9 Forge, and 1.7.10 Forge). This isn't a problem with the Mojang servers as they say they are up and I can authenticate for single player games. It isn't a reachablity problem either. I grabbed a tcpdump from the server (below) which shows the client connecting, the server doing a dns lookup for sessionserver.mojang.com and getting a response, then the server establishing a tcp session to sessionserver.mojang.com (with packets going back and forth).

Any ideas? Any pointers on how to get further debugs to see why the sessionserver.mojang.com is rejecting authentication attempts from my server?

12:24:18.580241 IP minecraft-client.55502 > minecraft-server.25565: Flags [S] , seq 1563706838, win 8192, options [mss 1460,nop,wscale
8,nop,nop,sackOK], lengt
12:24:18.580287 IP minecraft-server.25565 > minecraft-client.55502: Flags [S.], seq 3267555434, ack 1563706839, win 29200, options [mss
1460,nop,nop,sackOK,no
12:24:18.582210 IP minecraft-client.55502 > minecraft-server.25565: Flags [.], ack 1, win 256, length 0
12:24:18.582245 IP minecraft-client.55502 > minecraft-server.25565: Flags [P.], seq 1:33, ack 1, win 256, length 32
12:24:18.582259 IP minecraft-server.25565 > minecraft-client.55502: Flags [.], ack 33, win 229, length 0
12:24:18.582266 IP minecraft-client.55502 > minecraft-server.25565: Flags [P.], seq 33:48, ack 1, win 256, length 15
12:24:18.582273 IP minecraft-server.25565 > minecraft-client.55502: Flags [.], ack 48, win 229, length 0
12:24:18.583884 IP minecraft-server.25565 > minecraft-client.55502: Flags [P.], seq 1:174, ack 48, win 229, length 173
12:24:18.635129 IP minecraft-client.55502 > minecraft-server.25565: Flags [.], ack 174, win 255, length 0
12:24:18.685399 IP minecraft-client.55502 > minecraft-server.25565: Flags [P.], seq 48:311, ack 174, win 255, length 263
12:24:18.689617 IP minecraft-server.3716 > google-public-dns-a.google.com.domain: 52290+% [1au] A? sessionserver.mojang.com. (53)
12:24:18.689739 IP minecraft-server.2335 > google-public-dns-a.google.com.domain: 28589+% [1au] AAAA? sessionserver.mojang.com. (53)
12:24:18.722580 IP minecraft-server.25565 > minecraft-client.55502: Flags [.], ack 311, win 237, length 0
12:24:18.738401 IP google-public-dns-a.google.com.domain > minecraft-server.2335: 28589 0/1/1 (134)
12:24:18.801243 IP google-public-dns-a.google.com.domain > minecraft-server.3716: 52290 1/0/1 A 54.192.16.139 (69)
12:24:18.801618 IP minecraft-server.49472 > server-54-192-16-139.iad12.r.cloudfront.net.https: Flags [S], seq 87797192, win 29200, options [mss
1460,sackOK,TS val 4
12:24:18.923239 IP server-54-192-16-139.iad12.r.cloudfront.net.https > minecraft-server.49472: Flags [S.], seq 3076233143, ack 87797193, win 14480,
options [mss 146
12:24:18.923272 IP minecraft-server.49472 > server-54-192-16-139.iad12.r.cloudfront.net.https: Flags [.], ack 1, win 229, options [nop,nop,TS val
44812127 ecr 21518
12:24:18.924479 IP minecraft-server.49472 > server-54-192-16-139.iad12.r.cloudfront.net.https: Flags [P.], seq 1:146, ack 1, win 229, options
[nop,nop,TS val 448121
12:24:19.045243 IP server-54-192-16-139.iad12.r.cloudfront.net.https > minecraft-server.49472: Flags [.], ack 146, win 61, options [nop,nop,TS val
2151811653 ecr 44
12:24:19.048443 IP server-54-192-16-139.iad12.r.cloudfront.net.https > minecraft-server.49472: Flags [P.], seq 1449:2783, ack 146, win 61, options
[nop,nop,TS val 2
12:24:19.048472 IP minecraft-server.49472 > server-54-192-16-139.iad12.r.cloudfront.net.https: Flags [.], ack 1, win 251, options [nop,nop,TS val
44812158 ecr 21518[s][s][s][s]
[/s][/s][/s][/s]

Problem solved. It was an MTU problem on my hosting end that was dropping packets.