Four unknown switchports on a 24 port switch

Cadeyrn · ‎09-21-2021

Hi. I am setting up a newly provisioned Catalyst 1000 (C1000-24T-4X-L). It has 24 gigabit ports and 4 10G SFP+ uplinks. Here is the interface output:

SW01#show ip int brief
Interface              IP-Address      OK? Method Status                Protocol
Vlan1                  10.10.0.254     YES manual up                    up
Vlan10                 10.10.10.254    YES manual up                    up
Vlan20                 10.10.20.254    YES manual up                    up
Vlan30                 10.10.30.254    YES manual up                    down
Vlan40                 10.10.40.254    YES manual up                    up
GigabitEthernet1/0/1   unassigned      YES unset  down                  down
GigabitEthernet1/0/2   unassigned      YES unset  down                  down
GigabitEthernet1/0/3   unassigned      YES unset  up                    up
GigabitEthernet1/0/4   unassigned      YES unset  down                  down
GigabitEthernet1/0/5   unassigned      YES unset  up                    up
GigabitEthernet1/0/6   unassigned      YES unset  down                  down
GigabitEthernet1/0/7   unassigned      YES unset  down                  down
GigabitEthernet1/0/8   unassigned      YES unset  down                  down
GigabitEthernet1/0/9   unassigned      YES unset  down                  down
GigabitEthernet1/0/10  unassigned      YES unset  down                  down
GigabitEthernet1/0/11  unassigned      YES unset  down                  down
GigabitEthernet1/0/12  unassigned      YES unset  down                  down
GigabitEthernet1/0/13  unassigned      YES unset  up                    up
GigabitEthernet1/0/14  unassigned      YES unset  up                    up
GigabitEthernet1/0/15  unassigned      YES unset  up                    up
GigabitEthernet1/0/16  unassigned      YES unset  down                  down
GigabitEthernet1/0/17  unassigned      YES unset  down                  down
GigabitEthernet1/0/18  unassigned      YES unset  down                  down
GigabitEthernet1/0/19  unassigned      YES unset  up                    up
GigabitEthernet1/0/20  unassigned      YES unset  down                  down
GigabitEthernet1/0/21  unassigned      YES unset  up                    up
GigabitEthernet1/0/22  unassigned      YES unset  down                  down
GigabitEthernet1/0/23  unassigned      YES unset  down                  down
GigabitEthernet1/0/24  172.16.1.1      YES manual down                  down
GigabitEthernet1/0/25  unassigned      YES unset  down                  down
GigabitEthernet1/0/26  unassigned      YES unset  down                  down
GigabitEthernet1/0/27  unassigned      YES unset  down                  down
GigabitEthernet1/0/28  unassigned      YES unset  down                  down
Te1/0/1                unassigned      YES unset  down                  down
Te1/0/2                unassigned      YES unset  down                  down
Te1/0/3                unassigned      YES unset  down                  down
Te1/0/4                unassigned      YES unset  down                  down
Loopback0              10.10.1.2       YES manual up                    up

Gi1/0/1 through Gi1/0/24 are the expected 24 gigabit ports. And Te1/0/1 through Te1/0/4 are the 10G SFP+ ports.

But what are Gi1/0/25, Gi1/0/26, Gi1/0/27, and Gi1/0/28?

Thank you.

marce1000 · ‎09-21-2021

- Ref : https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst1000/hardware/installation/24_48_port_hig/b_c1000_24_48_hig/product_overview.html#concept_yfv_cwm_ckb

Have a look at Table 3 , probably relates to port/speed mode according to sfp-type.

M.

-- ' 'Good body every evening' ' this sentence was once spotted on a logo at the entrance of a Weight Watchers Club !

Deepak Kumar · ‎09-21-2021

It is port mapping as

Port Switch models1-GigabitEthernet ports 10-GigabitEthernet ports

GigabitEthernet1/0/25 ----> TenGigabitEthernet1/0/1

GigabitEthernet1/0/26 ----> TenGigabitEthernet1/0/2

GigabitEthernet1/0/27 ----> TenGigabitEthernet1/0/3

GigabitEthernet1/0/28 ----> TenGigabitEthernet1/0/4

Regards,
Deepak Kumar,
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Cadeyrn · ‎09-23-2021

Thanks for the response.

What is the need for this port mapping? What is the purpose and what is being achieved by this mapping?

Surely a 10 Gb port cannot be mapped to a 1 Gb port without a lose in bandwidth.

Or is just a logical mapping when running at 1 Gb speeds? When running at 10 Gb, is the mapping not used?

If a possible a little more background may help me understand this answer.

Thank you.

paul driver · ‎09-22-2021

Hello

you can use either 1gb or 10gb sfps in those ports

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Kind Regards
Paul

Cadeyrn · ‎09-23-2021

Yes, that is my understanding as well.

But I am understanding the relationship between the SFP+ ports and Gi1/0/25 - 28.

What is the purpose of this mapping, and what is being accomplished by doing it?

Is it just a logical mapping / internal implementation, or is it something that I should understand as an administrator?