Cisco Support Community
cancel
Showing results for 
Search instead for 
Did you mean: 
New Member

What cable? ASA to 3750 trunk?

Hello,

I have a ASA 5520 and will need to create a trunk to a 3750 from the one of the ASA's gigabit ports, this will allow me to create sub-interfaces on the ASA and use multiple VLAN's on the switch.  For the trunk do I need to use a crossover or straight-through?  I know switch-toswitch is crossover due to what pins they send and receive on, but am not sure with the ASA.  To be honest I think on another setup I have used a straight-through and it has worked, but would just like to know.

Thanks.

14 REPLIES
Hall of Fame Super Blue

Re: What cable? ASA to 3750 trunk?

Whiteford wrote:

Hello,

I have a ASA 5520 and will need to create a trunk to a 3750 from the one of the ASA's gigabit ports, this will allow me to create sub-interfaces on the ASA and use multiple VLAN's on the switch.  For the trunk do I need to use a crossover or straight-through?  I know switch-toswitch is crossover due to what pins they send and receive on, but am not sure with the ASA.  To be honest I think on another setup I have used a straight-through and it has worked, but would just like to know.

Thanks.

Andy

Straight-through is the cable you need.

Jon

Hall of Fame Super Gold

Re: What cable? ASA to 3750 trunk?

Straight-through or cross-over doesn't matter because the 3750 is MDI/MDI-X capable.  Just make sure that "no mdix auto" is not found in the port configuration of the switch.   As standard, I agree with Jon, use straight-through.

New Member

Re: What cable? ASA to 3750 trunk?

Thanks, what is MDI/MDI-X capable?

Hall of Fame Super Blue

Re: What cable? ASA to 3750 trunk?

Whiteford wrote:

Thanks, what is MDI/MDI-X capable?

It means the switch can detect which pins need to be switched around, so if you use a crossover where a straight-thru is needed the switch can adjust which pins are used to transmit and receive on the cable.

Jon

Hall of Fame Super Gold

Re: What cable? ASA to 3750 trunk?

jon.marshall wrote:

It means the switch can detect which pins need to be switched around, so if you use a crossover where a straight-thru is needed the switch can adjust which pins are used to transmit and receive on the cable.

Jon

Takes the fun out, huh Jon? 

Hall of Fame Super Blue

Re: What cable? ASA to 3750 trunk?

leolaohoo wrote:

jon.marshall wrote:

It means the switch can detect which pins need to be switched around, so if you use a crossover where a straight-thru is needed the switch can adjust which pins are used to transmit and receive on the cable.

Jon

Takes the fun out, huh Jon? 

It does doesn't it. I'm one of those people who began quite a while before auto-mdix came in and i still forget abou it and so spend half my time trying to find a crossover cable and you know you can never find one when you need one.

Last place i worked i got fed up with never being able to find a crossover so i ordered 20 of them to keep at my desk. 2 days later and they had all gone - thieving network implementation engineers

Jon

New Member

we are using asa firewall and

we are using asa firewall and other end is switch 3750 all the port are gigabit but in firewall all the port are ethernet. in ethernet:speed 100, duplex full..but in   switch end: auto is configured...we can configured like this;asa firewall e0/0 speed10, duplex full same as in the switch:g2/0/1:speed 10 duplex full. can we but it will work like half duplex..can any one assist me.     thanks natarajan.
Hall of Fame Super Gold

Re: What cable? ASA to 3750 trunk?

Is the ports for the ASA MDI/MDI-X?

Cisco Employee

Re: What cable? ASA to 3750 trunk?

Yes.

http://www.cisco.com/en/US/docs/security/asa/asa80/configuration/guide/intrface.html#wp1048058

Auto-MDI/MDIX Feature

For RJ-45 interfaces on the ASA 5500 series adaptive security appliance, the default auto-negotiation setting also includes the Auto-MDI/MDIX feature. Auto-MDI/MDIX eliminates the need for crossover cabling by performing an internal crossover when a straight cable is detected during the auto-negotiation phase. Either the speed or duplex must be set to auto-negotiate to enable Auto-MDI/MDIX for the interface. If you explicitly set both the speed and duplex to a fixed value, thus disabling auto-negotiation for both settings, then Auto-MDI/MDIX is also disabled. For Gigabit Ethernet, when the speed and duplex are set to 1000 and full, then the interface always auto-negotiates; therefore Auto-MDI/MDIX is always enabled and you cannot disable it.

-KS

Cisco Employee

Re: What cable? ASA to 3750 trunk?

If you connect two layer 3 devices  - use cross over - Example PC to Router

If you connect a layer 3 to a layer 2 - use straight through - Example PC to switch

-KS

Cisco Employee

Re: What cable? ASA to 3750 trunk?

Hello

Unless you hard set the speed/duples on ASA ports, they have auto mdix enabled by default. So no need to worry which kind of cable you gotta use.

BUT, once you hard set speed/duplex on any ifc, auto features is gone.

Thanks,

Vijaya

New Member

Re: What cable? ASA to 3750 trunk?

Thanks, normally a switch-to-switch uses a crossover cable, so am I rightis saying then a 3750 to 2960 trunk could use a straight through?

New Member

Re: What cable? ASA to 3750 trunk?

Whiteford wrote:

Thanks, normally a switch-to-switch uses a crossover cable, so am I rightis saying then a 3750 to 2960 trunk could use a straight through?

Andy,

To confirm, both the 3750 and the 2960 are switches, so without the auto-MDI/MDI-X, you would have to have a crossover.  If you leave the ports set to auto-negotiate, then yes, the 3750 to 2960 trunk could use a straight through.

Regards,

Jeff

New Member

Re: What cable? ASA to 3750 trunk?

Jon -

I keep some SuperLoopers in my bag of tricks for console, cross-over and loopback.  They will convert any straight through to the pinouts of the connector you add.  Very handy!!  Purchase here:

http://www.smartronixstore.com/index.cfm?fuseaction=category.display&category_ID=1&CFID=331701&CFTOKEN=66374228

Also, similar to other comments, if you're connecting devices that operate at the same layer in the OSI model, use a cross-over.  If they are different, use a straight-through.  That's not always so easy to determine, but serves well for things like switch/switch, router/router, pc/pc, etc. all of which would use cross-over.

3533
Views
5
Helpful
14
Replies
CreatePlease to create content