Fragmentation of IP packet with flag [DF]

Issues related to configuring your network
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vsg
Posts: 1
Joined: 2019/11/29 10:35:33

Fragmentation of IP packet with flag [DF]

Post by vsg » 2019/11/29 10:53:49

Prompt, for what reason the IP packet with the established flag [DF] can be fragmented?
[***@copy-m9 ~]$ uname -r
3.10.0-1062.4.1.el7.x86_64
We are testing a new transport Protocol with ip-proto=250.

Traffic dump:
.098508 IP (id 22113, offset 0, flags [DF], proto (250), length 1072) copy-m9 > copy-k4: ip-proto-250 1052
.098877 IP (id 22114, offset 0, flags [+], proto (250), length 748) copy-m9 > copy-k4: ip-proto-250 728
.098896 IP (id 22114, offset 728, flags [none], proto (250), length 742) copy-m9 > copy-k4: ip-proto-250

date size 1052 Bytes
fragm.1 728 Bytes
fragm.2 1052-728=324 Bytes
Where from 742-324-20(IP)=398 bytes ???

Thanks.

aks
Posts: 2859
Joined: 2014/09/20 11:22:14

Re: Fragmentation of IP packet with flag [DF]

Post by aks » 2019/12/01 17:16:38

What network(s) are you going over?
Ever heard of MTU?
Also if it's TCP, check the advertised windows, we have to fragment is there is insufficient resources to not fragment (on both sides).

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