topic Re: About MTU of CSC-SSM on ASA in Network Security

About MTU of CSC-SSM on ASA

STM_51 — Mon, 11 Mar 2019 20:03:26 GMT

I am using a ASA with CSC-SSM.

Is it correct that MTU of eth0 is 1796?
Is there an influence in the communication?

#@ Ethernet Interface Information
＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝
eth0      Link encap:Ethernet HWaddr 00:00:00:02:00:02
          UP BROADCAST RUNNING MULTICAST MTU:1796 Metric:1
          RX packets:200024351 errors:0 dropped:0 overruns:0 frame:0
          TX packets:215388556 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:4113709994 (3.8 GiB) TX bytes:3588690813 (3.3 GiB)
          Base address:0xcc00 Memory:f8100000-f8120000

eth1      Link encap:Ethernet HWaddr 00:19:E8:2B:C9:7A
          inet addr:10.21.1.63 Bcast:10.21.1.255 Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          RX packets:10705829 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1457926 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100
          RX bytes:1599212156 (1.4 GiB) TX bytes:185586566 (176.9 MiB)
          Base address:0xbc00 Memory:f8200000-f8220000
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＝＝＝＝＝ System info ＝＝＝＝＝＝
ASA Version 7.2(4)30
Device Manager Version 5.2(4)

Model:              ASA-SSM-CSC-10
Hardware version:   1.0
Firmware version:   1.0(11)2
Software version:   CSC SSM 6.3.1172.0
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Best Regards,

Re: About MTU of CSC-SSM on ASA

PAUL GILBERT ARIAS — Wed, 09 Mar 2011 14:36:55 GMT

somehow that interface has that MTU value. Is that the interface of the ASA itself?

Re: About MTU of CSC-SSM on ASA

STM_51 — Wed, 09 Mar 2011 14:50:46 GMT

Thank you for your reply.

No. The interface is CSC-SSM module's inter

face on ASA.

eth1 is a port of RJ-45type on CSC-SMS.

the interface has IP address and MTU:1500.

I think eth0 is a internal BUS to ASA.

eth0 has no IP address and MAC address is

00:00:00:02:00:02.

Re: About MTU of CSC-SSM on ASA

PAUL GILBERT ARIAS — Wed, 09 Mar 2011 15:08:14 GMT

yes, eth1 is the management interface for the module. eth0 should be the one on the backplane of the ASA but still don't know for sure why the MTU is higher.

I checked another CSC-SSM on a ASA5510 and it has the same value. No idea why.

Re: About MTU of CSC-SSM on ASA

STM_51 — Wed, 09 Mar 2011 15:23:25 GMT

Hi Paul

Thank you for confirming it.

Does not your ASA(CSC) has a communication trouble?

For example, DELAY or Packet Loss ....

Re: About MTU of CSC-SSM on ASA

PAUL GILBERT ARIAS — Wed, 09 Mar 2011 15:29:06 GMT

no troubles so far. are you sending high loads of traffic to the CSC?

Re: About MTU of CSC-SSM on ASA

STM_51 — Wed, 09 Mar 2011 15:52:49 GMT

I don't send high loads of traffic. Your CSC's eth0 is 1796 , isn't it?

So, MTU:1796 is no problem, isn't it?

Our trouble is occurred on communication to a part of URL.

If the MTU value has some problems, it is occurred trouble on all communications, I think.

Maybe this MTU is no problem.

I want to think it.

Re: About MTU of CSC-SSM on ASA

PAUL GILBERT ARIAS — Wed, 09 Mar 2011 16:01:16 GMT

same MTU but no problems. I don't think MTU is your issue.

Re: About MTU of CSC-SSM on ASA

STM_51 — Wed, 09 Mar 2011 16:32:16 GMT

Thank you so much.