internet 3945

[Mlex1]

Hello, i have Cisco router 3945, working well, when i reboot or after electricity goes down internet doesn't working, i should go to router do shutdown and no shutdown after internet will working.

why does this happen thanks in advance 

[liviu.gheorghe]

Hello @Mlex1 ,

can you provide some more details regarding the router itself? Can you share the config and the show version?

[Mlex1]

flash0:c3900e-universalk9-mz.SPA.157-3.M8.bin

Can you share the config and the show version?

can't share secret i can share part of config 

[liviu.gheorghe]

---

@Mlex1 wrote:

flash0:c3900e-universalk9-mz.SPA.157-3.M8.bin

Can you share the config and the show version?

can't share secret i can share part of config 

---

Don't need passwords to troubleshoot the problem.

[M02@rt37]

Hello @Mlex1 

As concerned this specific interface facing "internet", is it a manual or dhcp ip address ?

[Mlex1]

manual 

[M02@rt37]

Ok @Mlex1 

The router's routing table or ARP cache might not be getting populated correctly after a reboot. Manually restarting the interfaces may trigger the process of updating these tables.

[Mlex1]

i will emulate this moment next week, thanks for support

[Mlex1]

here i didn't see any changes with arp table but my default route disappear, also i see errors on port where cable from provider connect to my switch.

R1#show interfaces gigabitEthernet 1/1/1 | S runts
9 runts, 0 giants, 0 throttles

[JordanHall]

It sounds like you might be experiencing an issue with the Cisco router not automatically restoring internet connectivity after a reboot or power outage. This could be due to various reasons, and here are a few common possibilities:

1. Interfaces not coming up: After a reboot or power outage, the interfaces on the router may not be coming up automatically. You can check the status of the interfaces by using the show ip interface brief command. Make sure that the relevant interfaces are in the "up" state.

2. Configuration not saved: If the router is not saving its configuration, any changes made during the session may be lost after a reboot. Ensure that you are saving the configuration using the write memory or copy running-config startup-config command.

3. IP addressing issues: There could be issues with obtaining IP addresses for the interfaces, especially if they rely on DHCP. Make sure that DHCP is configured correctly or check the static IP settings if applicable.

4. Routing issues: After a reboot, the routing table might not be repopulated correctly. Verify that the routing information is accurate using the show ip route command.

5. Software or firmware issues: Ensure that your router is running the latest stable software or firmware version. Bugs in the operating system might be causing the issue, and updating to the latest version could resolve it.

[Mlex1]

Interfaces not coming up:

ConfiguratioRouting issues:

all good

mansion above my default route disappear

[Mlex1]

i don't know how to solve this problem if i know i will share menеioned here, currently i solve this problem via shutdown and no shutdown
i will close the ticket thanks in advance

[Richard Burts]

You may close the ticket if you want. Or if you want to go a bit further with it I would suggest that after the next reboot, before you shut/no shut perform these commands and post the output

show ip interface brief

show ip route

show arp

show interface

[Mlex1]

Hello Richard

with due all respect, i done all steps i only see one differents my default router disappear, after shut and no shut on port internet working internet.

Currently i'm waiting for ISP

1 They should change SFP modul

2 Connect our internet from another side 

result i will share thanks in advance 

[peytonjosie3]

It sounds like your Cisco router 3945 may be experiencing an issue where the internet connection fails to initialize properly after a reboot or power outage. This could be due to a configuration problem, interface flapping, routing or NAT issues, or even hardware malfunctions. By performing a shutdown and then a no shutdown on the affected interface, you're essentially resetting the connection and allowing it to reestablish properly. To address this issue, you should check for misconfigurations in the router's configuration file, verify the physical connection, review router logs for errors, test internet connectivity using diagnostic commands, and consider contacting your ISP for assistance. If the problem persists, further troubleshooting or consultation with Cisco technical support may be necessary to resolve the issue and ensure reliable internet connectivity.