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Catalyst Blade Switch 3020 (410916-B21)'s VLAN MTU

chuckk281
Trusted Contributor

Catalyst Blade Switch 3020 (410916-B21)'s VLAN MTU

A question from Yao:

 

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I have 2 questions about Catalyst Blade Switch 3020 (410916-B21).

According to below guide, system mtu jumbo’s range is 1500 to 9000 bytes and VLAN MTU range is 1500 to 18190.

http://www.cisco.com/en/US/docs/switches/blades/3020/software/release/12.2_58_se/configuration/guide/3020.pdf

301

system mtu bytes (Optional) Change the MTU size for all interfaces on

the switch that are operating at 10 or 100 Mb/s. The

range is 1500 to 1998 bytes; the default is 1500 bytes.

system mtu jumbo bytes (Optional) Change the MTU size for all Gigabit

Ethernet interfaces on the switch. The range is 1500 to

9000 bytes; the default is 1500 bytes.

 

320 page

Table 12-2 Ethernet VLAN Defaults and Ranges

MTU size range: 1500 to 18190

 

My questions are the following ones:

①  What’s the meaning of VLAN MTU?

②  What’s the relation between system MTU and VLAN MTU? For instance, should I set VLAN MTU bigger than system MTU?

 

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From Jim:

 

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I think these Catalyst IOS options are somewhat vestigial. The MTU maximum transmission unit (packet size, in bytes) that the VLAN can use (up to 18190) is for Token Ring or FDDI networks of the past as they could utilize the larger MTU’s, Ethernet networks are as you stated 1500 default and up to 9000 for jumbo configurations.

 

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Any other comments or suggestions?