×
INTELLIGENT WORK FORUMS
FOR COMPUTER PROFESSIONALS

Log In

Come Join Us!

Are you a
Computer / IT professional?
Join Tek-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Tek-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Cant get a simple 1 gig multimode fiber link to come up

Cant get a simple 1 gig multimode fiber link to come up

Cant get a simple 1 gig multimode fiber link to come up

(OP)
I am going nuts. This is something that I do all the time. The last 2 times I have tried it, I had the same problem.  HP Networking s7910 (like the 7500 switch, just before HP renamed it).  going from a 1gig SFP gbic to another 1gig SFP Gbic - IN THE SAME ROOM.

Read this before replying and telling me to swap the connectors on one end of the link....

Here is what I've tried:

1.    Different fiber patch cables
2.    Different GBICs in our core
3.    Different PORTS in our core
4.    I can loop the Core side & I get a link
5.    I can loop the Comcast side & I get a link
6.    I tried forcing the speed to 1gig on the Core side (but that shouldn't impact a physical link)
7.    I can get a link from the WAN port on the Core to another GBIC on the core switch
8.    The Comcast box always gets a link when connected to the core, Our side does not.

I can see red light coming from the Comcast GBIC.
I can see red light coming from the Core GBIC.
I made sure the red light coming from us goes to the dark side on the Comcast Box.

 

RE: Cant get a simple 1 gig multimode fiber link to come up

(OP)
Here is the Answer:
Even though its just a physical link, the 3Com/HP Networking A-Series to <any-other> requires a hard coded speed AND DUPLEX setting before the link light will come on.

For a 1Gig, full duplex connection:

Interface Gigabit n/n/n
port access vlan xxx
speed 1000
duplex full

Other switches will show a link light when they see light from the other side in the right wavelength.

RE: Cant get a simple 1 gig multimode fiber link to come up

Yes, you get no physical connectivity unless you set both sides to 1000/Full instead of auto.
 
Unless you're using 1Gb SFPs in SFP+ slots, in which case it only works if set to auto(!).  

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Tek-Tips Forums free from inappropriate posts.
The Tek-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Tek-Tips forums is a member-only feature.

Click Here to join Tek-Tips and talk with other members!

Close Box

Join Tek-Tips® Today!

Join your peers on the Internet's largest technical computer professional community.
It's easy to join and it's free.

Here's Why Members Love Tek-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close