is there any restriction with one eHWIC-4ESG-P (POE) on 1921 ?

[nlariguet]

I have a 1921 which had a HWIC-4ESP (the older FastEthernet) installed and then I installed a newer eHWIC-4ESG-P alongside.

When I did not see any Gigabit interfaces for the newer eHWIC-4ESG-P I came across this document stating that it won't work alongside the older switch card nor alongside another identical card since the 1921 has no backplane and the switch cards connect directly to the processor via SerDes or something like it.

https://www.cisco.com/c/en/us/td/docs/routers/access/interfaces/software/feature/guide/geshwic_cfg.html

https://community.cisco.com/t5/switching/cisco1921-k9-wic-slot-1-unknown-4-port-ge-switch/td-p/3211012

So, I removed my older FastEthernet card and left the newer eHWIC-4ESG-P alone but I can't manage to see any interfaces yet no matter which port I place the card in.

router is C1921/K9 chassis hardware revision 01

bootstrap is 15.0.1r.M16

IOS is 15.8.3.M5

eHWIC-4ESG-P is shown in show inventory

Maybe because the card is the POE version ?

[Leo Laohoo · Accepted solution]

If the router does not have a bigger power supply, that PoE line card will not boot. 

Look at the power supply and see if there is a "phone" icon.  The icon is usually found next to the power switch.  If the icon does not have a phone icon, then the power supply is a "regular" one.

[nlariguet]

Ahhh guessing this is the small letter buried-sooo-deep-in-the-manual that Cisco is famous for. Tons of useless and obvious wording in the manuals and what really matters you have to look very deep to find.

Well, anyway I suppose this explains the cause, there are lots of posts in these forum on the eHWIC-4ESG not showing its interfaces and none of them mention this "subtle" fact.

And no, my router does not have this phone icon on its PSU.

Thank you very much for your reply leo !