Connecting ASA5520 to a 3750G SFP port

[phillh1974]

Hi All.

I have always connected switch SFP uplink ports via fibre to a core 6500 fibre blade. What I am wondering is whether a copper SFP on a C3750G can be used to uplink from an ASA Ethernet port, G0/2?

This is how I've connected in my home lab and I cannot get the link live.

I have the ASA and 3750 SFP ports set to Auto/1000 and cannot get the link up, I've also issued the error disable command on the SFP port but still cannot get the link up.

Would it be a better practice to connect the ASA to an Ethernet port on the switch?

Thanks for any advise you can offer.

Phill

[balaji.bandi]

it should work expected below sample config to test : or post the configuration of both the device :

SW :

vlan 50

name ASA

interface vlan 50

ip address 1.1.1.1 255.255.255.0

interface gig 1/1

description Link to ASA

switchport mode access

switch port access vlan 50

spannning-tree portfast

no shut

ASA

interface gig 0/2

nameif inside

security level 100

ip address 1.1.1.2 255.255.255.0

no shut

connect the cable and test it.

if still not working

post the confguration along with show interface on both the sides.

[phillh1974]

Hi Balaji.

Thank you for your response.

Please see attached for device configurations applied.

Many Thanks

Phill

[Georg Pauwen]

Hello,

the ASA 5520 doesn't have any SFP fiber ports, so copper is your only option. What cable are you currently using to connect the ASA to the 3750 ? 

[phillh1974]

Hi.

I'm looking to connect the 3750 copper SFP GI1/0/27 to the ASA 5520 Ethernet port Gi0/2.

There are no SFP ports available on the ASA.

I know the norm is for SFP to SFP, just wondered if it was possible to go standard Ethernet to copper SFP?

Thanks

[Reza Sharifi]

Hi,

Copper SFP (GLC-T) should work fine on 3750G. See link:

https://www.fs.com/products/11773.html

HTH

[phillh1974]

Hi Reza.

That's the exact SFP transceiver I have installed into the 3750 but no link. Both ASA and 3750 ports are status down down.

Is this likely to be a duplex negotiation issue? I have both ports set to duplex auto / speed 1000.

I've disabled error disable just incase the port had disabled itself but no change and shut / no shut makes no change.

All of the cisco literature I've read is based around connecting SFP to SFP.

Thanks

[Georg Pauwen]

Hello,

is the GLC-T working at all ? Can you (successfully) connect another device to that GLC-T, using the same cable ?

[phillh1974]

Hi Georg.

The GLC-T is working ok as is the patch lead in use, the patch lead was tested by up linking the switch to the ASA using port Gi1/0/1.

Thanks

Phill

[balaji.bandi]

I do not see any config issue here

1. Try changing the patch lead and test with otehr device make sure the patch is ok.

2. try nonegotiate on ASA side also see if that makes any difference.

3. Try different port and check both ports working as expected?

[phillh1974 · Accepted solution]

Hi Balaji.

The patch lead was tested and works ok.

I ended up setting the 3750 Gi1/0/27 interface back to default configuration, setup the port up as a trunk link and issued the switchport nonegotiate command on the interface. I then configured gi1/1/25 combi port on my SG500 and patched to the ASA Gi0/2 interface to test the SFP and confirm correct operation, this worked first time.

I then connected the ASA Gi0/2 port back into the 3750G Gi1/0/27 SFP interface and still no link, by setting the ASA Gi0/2 interface to speed and duplex auto the link came live. To further verify the cause of the issue I removed the switchport nonegotiate config and the link remained live and stable.

To confirm the issue was with setting the ASA Gi0/2 to 1000/Full, it needed to be Auto/Auto to work.

Thank you for your responses, very much appreciated.

Phill

[balaji.bandi]

Thanks for the input, Glad all working as expected.