Questions tagged [cisco-ios]

For discussion about Cisco's Internetwork Operating System - Cisco IOS

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4 votes
1 answer
1k views

Config logging on which cisco IOS?

I want to configure configuration logging on network devices by running following commands. archive log config logging enable I want to know which Cisco IOS and device support it? I used cisco ...
  • 311
2 votes
1 answer
1k views

Unable to enable "Directed broadcast" on router in packet tracer?

I have a topology like below, wherein 2 subnets with address 192.168.0.0/24 and 192.168.1.0/24 are connected to a single router, Router0. Now i want to send a directed broadcast from PC0 on subnet ...
  • 677
2 votes
2 answers
103 views

No internet through router

I have the following network setup, but on the computer I can't access anything that's outside of the TP-Link router. When I tried to ping 8.8.8.8, I got reply from 192.168.2.1:Destination Host ...
3 votes
1 answer
6k views

IPsec Tunnel is showing decrypt packets counter but 0 encryption packets: #pkts encaps: 0, #pkts encrypt: 0, #pkts digest: 0

I have just configured the IPSEC tunnel between my router and the Access point.I could see that the Tunnel has came up and Active in both sides. However,When I checked the "Show cyrpto ipsec sa" ,I ...
  • 1,362
1 vote
1 answer
195 views

Extended ACL not working with "host"-Attribute in Cisco Packet Tracer

Here's the output (or the commands) which fails: Normally it should work! What's wrong here?
  • 772
1 vote
1 answer
263 views

IPv6 ACL in Packet Tracer - why doesn't it work?

I typed in this command: ipv6 access-list NO-SERVER-ACCESS permit ipv6 2001:db8:18::/48 host 2001:db8:18:6600::0010 eq 80 permit ipv6 2001:db8:18::/48 host 2001:db8:18:6600::0010 eq 443 permit ...
  • 772
1 vote
2 answers
369 views

Cisco IPSEC Tunnel with hidden local networks

I've got an ipsec tunnel that's up and working with ATT. They require that the phase 2 IP's not be local LAN's, but public IP's. So, my phase 1 is X.X.X.132, and my Phase 2 is on the same subnet as X....
  • 11
0 votes
2 answers
1k views

Stateful DHCPv6 Default Router

I understand that stateful DHCPv6 cannot provide hosts with a default router, as DHCPv4 could. Hosts would need to determine the default router based off of the information in RA packets. In my lab, ...
1 vote
1 answer
141 views

Where did `private_sg-0` come from?

I'm configuring my first Cisco product (WS-C3560CX-12TC-S) and trying to get to grips with aaa. I'm used to *nix where the first thing you do with headless devices is enable and configure SSH access ...
1 vote
1 answer
130 views

IP SLA with follow on actions

Good day, I have an odd one here. I am wanting to run an IP SLA to ping another device in the network, and if it stops responding, or the interface goes into a down state. I would like it to run a ...
  • 31
2 votes
2 answers
2k views

Can't use "dot1x" command in Cisco Packet Tracer

I am trying to configure 802.1X authentication on a Cisco switch 2960 in Cisco Packet Tracer software. Here I found the offical guide: https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst2960/...
  • 123
5 votes
2 answers
4k views

Changing The Stack Master of a Catalyst 3750 Without Losing Connection

Currently I have 5 Catalyst 3750 V2-48TS as slaves and 1 Catalyst 3750g 24TS-1U as the Stack Master. I was wondering if there was any way to change the Stack master to one of the slaves without ...
1 vote
1 answer
934 views

Excessive "Failed to read module serial eeprom" on Catalyst 4507

I have a plethora of these messages %C4K_CHASSIS-3-LINECARDSEEPROMREADFAILED: Failed to read module 5's serial eeprom, try reinserting module on my Cisco Catalyst 4507R. Thing is, there's nothing ...
3 votes
2 answers
1k views

No passive-interface error

I'm trying to nest some EIGRP configurations on a router in GNS3. I'm trying to connect the EIGRP 2801 in SW01 to RTR-01 and EIGRP 2864 to RTR-02 when I do. When I put no passive-interface ...
  • 133
3 votes
1 answer
166 views

How to permit behaviour in Cisco access-list commands?

If a host on a network is permitted to access another host on a different network via an ACL on the source host's router, does that automatically deny other hosts on the same network as the source ...
4 votes
1 answer
6k views

Create a internal connection between ISR 4451 and EtherSwitch submodule

In a Cisco ISR 4451 we install a EtherSwitch 48 Port Module. The ISR is working and the EtherSwitch Module too. Now I want to create a route from ISR to EtherSwitch and read some Manuals and Forum ...
  • 423
5 votes
1 answer
7k views

When and where to use Spanning-Tree (Portfast)

The tl;dr, in which scenario (switch-to-host, or switch-to-switch) do I use spanning-tree portfast or spanning-tree ...? We had a catastrophic network outage today. My first question to my boss was "...
7 votes
1 answer
569 views

Cisco IOS Tcl - Overhead

I've not been able to find much in regards to TCL other than the Cisco PDF "Cisco IOS Scripting with TCL Configuration Guide" and I just have a few queries. I'm looking into potentially utilising ...
2 votes
1 answer
644 views

Cisco 871 router vlan configuration and Routing between interfaces

I'm planning to enable the connectivity with our access points as shown in the Diagram. I would like to understand how can I enable the routing between 192.168.1.1/25 (FE4)and 10.140.134.0/25(FE1). ...
  • 1,362
2 votes
1 answer
1k views

How to configure site to site VPN between Cisco ASA and Cisco router? [closed]

I have CISCO ASA on one site and CISCO ROUTER on other side, both have outside interface facing public IP and doing NAT for internal VLAN's. How to connect different VLAN's on one site to VLAN's on ...
  • 86
1 vote
1 answer
100 views

Why is my Cisco MMS891 assigning IP addresses with static NAT entries to devices via DHCP?

I have a Cisco MMS891 ISR as my edge router with several static NAT entries, which are set up to NAT my LAN IP addresses (which are statically assigned to printers) to access an externally hosted ...
3 votes
2 answers
2k views

Cisco IOS pick default route from two DHCP interfaces with track

I plan to have a portable IOS cisco router which will have two DHCP assigned ISP addresses from unknown ranges. A tunnel is then built through the preferred ISP to another outer. I would like to set ...
  • 227
1 vote
2 answers
766 views

Routers using RIP can't see their own route Serial Interface

I have two routers, R2 AND R3, I've configured the RIP with no auto-summary, the serial interfaces are registered too but the routers can't see them, in this case, R2 se0/0/1 and R3se0/0/1. How can I ...
  • 13
2 votes
2 answers
584 views

Manually set combo interface for RJ45 Cisco 3560-CG Series

I have a Cisco Catalyst 3560-CG that has two combo ports with SFP and RJ45 each. Is it possible to manually set the combo port to use the RJ45 only? If so, how is it done? I am troubleshooting a ...
  • 315
1 vote
1 answer
167 views

Return traffic for nonzone interfaces in Cisco IOS (ZBFW)

I've found Cisco docs to be extremely vague and confusing regarding the appropriate way to configure access policies in Cisco IOS-based zone-based firewall (ZBFW). Say I want to permit ongoing TCP ...
1 vote
2 answers
470 views

3502i no console output, how to properly diagnose?

I have purchased an old cisco 3502i AP from good old ebay. I'm trying to set it up, but am not receiving anything over a console connection. I'm using the exact same USB adapter & console cable ...
  • 111
1 vote
1 answer
363 views

How to mirror the WAN port of a Cisco 871 router?

I have setup one IPv6 6to4 tunnel between two routers.The tunnel seems to be up and running and I'm able to ping from Router R1 to R2 as well. However,I would like mirror the WAN port to see the ...
  • 1,362
7 votes
2 answers
7k views

Cisco 3064 switch upgrade from 6.0.x to 7.0.x issue

I am trying to upgrade from 6.0.2.U6.5c to nxos.7.0.3.I4.7, before upgrade i want to make sure it pass all checks but i got this error. This switch isn't in production yet but want to make sure it ...
  • 4,257
2 votes
2 answers
428 views

Cisco C800 - keep bridge interface up even when no active connections

Due to our clunky monitoring, we are watching an IP on a bridge interface on a Cisco C800, which sometimes won't have any active FastEthernet connections which means the bridge goes into the down ...
3 votes
1 answer
980 views

Routing Between VLANs on Cisco 1921

I have setup a new VLAN for VoIP phones that are being installed. I would like to segment their traffic to Subnet 10.20.77.0/24. I added an IP address to the DHCP server of 10.20.77.11 to help serve ...
2 votes
2 answers
2k views

PC can't ping router 2 hops away (home lab)

To give some context, here is my setup: ----(10.0.0.1 - S0/0/0) R1 (S0/1/0 - 10.0.1.1)---- | | | | ...
  • 135
1 vote
1 answer
1k views

Trying to figure out why Serial0/0/0 can't be pinged

Here's the setup: R1 -> R2 | |--> R3 R1 has 2 serial interfaces - Serial0/0/0 (10.0.0.1) is connected to R3 (Serial0/0/0 - 10.0.0.3), and Serial0/1/0 (10.0.0.4) is connected to R2 (Serial0/...
  • 135
1 vote
3 answers
250 views

Routing issue on router

I have created network with 3 routers, 3 switches and 6 computers Below are configurations, R1-> serial2/0= 192.168.1.1/30, Fastethernet 0/0= 192.168.1.9/29 R2->serial2/0= 192.168.1.2/30, ...
1 vote
3 answers
732 views

Cisco NAT of Source and Destination Addresses

I thought I had a relatively simple question, however I can't seem to find a solution online easily. My problem is: I have two Cisco 1941 routers configured each with their own direct internet facing ...
3 votes
1 answer
295 views

Cisco router under workgroup bridge AP

My question is about addressing a Cisco router interface so that I can use both bridging through an access point as workgroup-bridge and also connect to the access point to configure it. Apologies ...
  • 15.9k
1 vote
2 answers
10k views

Ping Vrf Loopback Interface

I'm doing a Lab and it's very simple. it's just like I need to confirm some commands but I'm really getting upset. here is my lab. I configured a vrf and a loopback interface which I apply it under ...
2 votes
1 answer
944 views

How to prevent IOS sending icmp unreachable with output ACL?

I have an output ACL applied on a WAN interface that permits only 1 IP from going out. interface Cellular0 ip address negotiate ip access-group allow100.98.170.25 out ip nat outside no ip ...
  • 252
2 votes
2 answers
544 views

Cisco 2911 - display location using the show line command

On a Cisco 2911 terminal server, if I run the command show line, it will present info about the console ports like this: 0/0/0 3 TTY 9600/9600 - - 3 - - 116 162 671/0 -...
5 votes
1 answer
1k views

Why is option 82 required for DHCP when you use `ip verify source port-security`?

Learning about security features on Cisco switches and came across the requirement to use option 82 with DHCP when you enable ip verify source port-security on an interface. How is this different ...
  • 26.9k
1 vote
3 answers
497 views

Cisco IOS - dropping all traffic not translated by NAT

I have a couple of rather basic questions about NAT translation. For a simple translation like: ip nat inside source list ACL interface GigabitEthernet 0 overload If the traffic does not match ACL, ...
  • 252
2 votes
1 answer
64 views

Is there any way to break a router's password?

I want to change the configuration of a router but a password has been set. Is there any way to troubleshoot, coz no one knows the exact password.
2 votes
3 answers
117 views

where does the running-config come from in a new fresh switch?

Generally, in a fresh switch, I see a startup-configuration. Switch#show startup-config startup-config is not present But when I do 'sh run' I see a default running config in it. Where does this ...
  • 55
2 votes
2 answers
3k views

Cisco IOS Switch: Why is "no spaning-tree vlan XXX" automatically inserted on vlan creation?

Yesterday we added a few VLANs (218-220) to one of our core-switches (WS-C3560X-24, c3560e-universalk9-mz.122-55.SE3 running as vtp-server) and noticed that a configuration directive no spanning-tree ...
2 votes
1 answer
168 views

Traffic not seen as interesting over tunnel

I have an issue where traffic is no longer passing over the tunnel. Below is my config and I can not get access to the other side due to not being allowed. I just need to make sure my config is ...
  • 195
2 votes
2 answers
2k views

Can I connect to Cisco router's AUX port from a switch Ethernet port?

I know from this question console connection via Cisco router's AUX port that it's possible to connect from a Cisco router to the switch/router's console port but I would like to know if it's ...
  • 145
1 vote
1 answer
2k views

How to enable SM-X Module in cisco ISR 4451 Router

While plug in a SM-X-ES3D-48-P Etherswitch Module into a Cisco ISR 4451 the Ports for this Module didn't came up. What I need to do to get the Ports enable with sh ip int br command? The Output of ...
  • 423
7 votes
2 answers
2k views

What is the difference between "ip domain name" and "ip domain-name"?

I'm running a ISR 4221 with "Cisco IOS XE Software, Version 16.04.02". I see that it has both ip domain name and ip domain-name commands. Why? Is this some sort of compatibility thing? My 7206 ...
1 vote
1 answer
1k views

Logging syncronous command unrecognized

I have a Cisco SG300-10 with software version 1.3.7.18. The switch is configured as a layer 3 device. I'm trying to stop the log message from interfering with my commands. I have tried to type logging ...
  • 13
1 vote
2 answers
3k views

What do the two different reload times mean in show version output?

We're rebooting several ASR920s from the command line (to upgrade the IOS) and a couple have failed to come back up at first. These two have very different times for returned to ROM and restarted. ...
  • 476
1 vote
1 answer
302 views

disable entering to enable mode IOS

Is it possible to disable entering an enable mode on IOS ? Im deploying radius servers with two user groups (lvl 1 and lvl 15) my goal is to do that users who are lvl 1 would be not permited to enter ...
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