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sectel
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c2921 router will not bring up fibre SFP

I can't get two cisco 2921 routers to talk to each other

the setup works find in my testbed with a rj45 cross over cable between them or even with a WANEM cloud emulator(free tool).

after migrating from CU  to fibre they won't to talk to each other anymore. worse, both refuse to bring up their wan side fibre SFP.
the "media-type" sub i/f command was used to change to SFP from RJ45
after that, the EN SFP light appears on both routers, but no link light

sh int gi 0/1
GigabitEthernet0/1 is down, line protocol is down
  Hardware is CN Gigabit Ethernet, address is xxx(bia xxx)
  Description: ** TEST LINK
  Internet address is 1.1.1.2/30
  MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 1000Mb/s, media type is SX
the two routers are in different buildings and must pass through a middle building(#2)

B1 - 200m -- B2 -- 900m -- b3

R1 (in building 1) is 200m from building 2
R2 (in building 3) is 900M from building 2

R1 has a MM SFP in Gi 0/1
R2 has a SM SFP in Gi 0/1 as the distance is too far for MM
in building two we have used both a SM to MM media converter
and a layer two switch with SM and MM SFP,
both show similar results

R1(MM sfp) --MMcable-- (MM sfp) switch (SM sfp) --SMcable--(SM sfp)R2

on the switch( in Bld 2), we see links lights coming out of the two routers, for both SM and MM links, this is good and expected. no traffic is seen though

on either router, no link light is seen and both interfaces are down down. shut, no shut, does not bring them up

we have tried different SFP and cables, still no change

one google search mentions an undocumented ciso command to ignore incompatible SFP, but that does not work is IOS 15

if we add a 3750 switch to the routers Gi 0/1 WAn side as a media converter, we get success. the switch has two sfp, one Cu and the other MM or SM fibre . the router "media-type" sub i/f command was used to change to RJ45 from SFP, after that, the SFP EN lights goes out(as expected) on both routers,

R1(CU)-(CU)3750(MM sfp) --MMcable-- (MM sfp) switch (SM sfp) --SMcable--(SM sfp)-(SM sfp)3750(CU)R2

why does this work and the connection on the rtr does not

sh int gi 0/1
GigabitEthernet0/1 is up, line protocol is up
  Hardware is CN Gigabit Ethernet, address is xxx(bia xxx)
  Description: ** TEST LINK
  Internet address is 1.1.1.2/30
  MTU 1500 bytes, BW 1000000 Kbit/sec, DLY 10 usec,
     reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, loopback not set
  Keepalive set (10 sec)
  Full-duplex, 1000Mb/s, media type is RJ45
this test is not practical in the deployed field and far too expensive

i am looking for a solution and want to know why the SFPs do not work in the routers

i tried two different MM SFP. neither one worked, though from SH INV, one can't tell them apart. on the CISCO site only this one is supported
glc-sx-mm, the SFP-GE-s is not supported on the 29xx rtr but is on the 3750 switch (;

================
%added SFP-GE-s SFP, the SFP-GE-s is not supported on the 29xx rtr but is on the 3750 switch
sh inv
NAME: "CISCO2921/K9 chassis", DESCR: "CISCO2921/K9 chassis"
PID: CISCO2921/K9      , VID: V03 , SN: xxxx

SFP-GE-s
NAME: "1000BASE-SX SFP", DESCR: "1000BASE-SX SFP"
PID: FTLF8519P2BNL-C6B , VID: B  , SN: xxxx
%============
%remove SFP and added glc-sx-mm SFP, this is the supported MM SFPO for the 29xx rtr
sh  inv

NAME: "1000BASE-SX SFP", DESCR: "1000BASE-SX SFP"
PID: SFBR-5766PZ-CS1   , VID:    , SN: xxx
============
Cisco IOS Software, C2900 Software (C2900-UNIVERSALK9-M), Version 15.0(1)M3, RELEASE SOFTWARE (fc2)  
Cisco CISCO2921/K9 (revision 1.0) with 475136K/49152K bytes of memory.
Processor board ID xxx
9 FastEthernet interfaces
3 Gigabit Ethernet interfaces
1 Virtual Private Network (VPN) Module
DRAM configuration is 64 bits wide with parity enabled.
255K bytes of non-volatile configuration memory.
500472K bytes of ATA System CompactFlash 0 (Read/Write)

License Info:
License UDI:
-------------------------------------------------
Device#   PID                   SN
-------------------------------------------------
*0        CISCO2921/K9          xxx
Technology Package License Information for Module:'c2900'
----------------------------------------------------------------
Technology    Technology-package          Technology-package
              Current       Type          Next reboot
-----------------------------------------------------------------
ipbase        ipbasek9      Permanent     ipbasek9
security      securityk9    Permanent     securityk9
uc            None          None          None
data          None          None          None

Configuration register is 0x2102

any suggestions or tips to check out
Switches / Hubs

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Last Comment
sectel

8/22/2022 - Mon
cstosgale

Are you using genuine Cisco transceivers? If not, I suspect this is the problem. Some Cisco devices are a lot more picky about exactly what transceivers they will work with. Here is a URL that shows what transceivers the 2921 is compatible with:

http://www.cisco.com/en/US/docs/routers/access/2900/hardware/installation/guide/Internal_Modules.html#wp1117361
sectel

ASKER
yes i am using real cisco SFP's. i agree they are very picky.
hp on the other hand does not care who made them. cisco needs cisco sfp's

i saw that page already,  thus i tried two types of SFP, see above. though from sho INV, you can't tell one sfp from the other
ASKER CERTIFIED SOLUTION
sectel

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sectel

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the root cause was found and a solution was identified to prevent this problem in the future
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