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18

I don't believe that there is anything simpler than show interfaces | <some regex> unfortunately. Edit: From the comments below, @Santino pointed out a more concise RegEx: show ip interface | include line protocol|access list My testing so far indicates that this gives the same results as my longer RegEx below. I usually use the following to find ...


15

You can configure an SVI as a dhcp client by using the following command within the SVI. ip address dhcp The same command is used on physical interfaces as well.


13

I wonder what can cause that the first line output of the command "show interfaces" will be: "fastEthernet is up, line protocol is down". Cisco ethernet interfaces are normally down / down if they don't have a link. If you're seeing up / down, the most likely causes are: Cable fault Speed mismatch (I personally haven't seen a duplex mismatch bring an intf ...


10

Your problem is that you are addressing in two separate networks: 216.21.5.0/31 and 216.21.5.2/31. The addresses you are using are in the same /30 network, but two separate /31 networks. You need to set one address as 216.21.5.0 and the other address as 216.21.5.1, or set one address as 216.21.5.2 and the other address as 216.21.5.3. The warning is because ...


10

While Ron and Ron's answers actually enable routing but prevent traffic, their suggestions still pack both host groups into the same routing instance. There's another way to think about this: a) VRF-lite This essentially creates two almost completely (well, they share the hardware ressources...) separated routing instances in one box. Things might get ...


8

It depends on routing table of router2 and other devices in your network (if you have any between router1 and router2). Router1 does not influence on it, it can be do something only when packet arrives to the its interfaces. It depends on routing table of router1, if you don't use any policy-based routing. So if router2 has address 10.232.92.101, for example,...


8

I was wondering if there was a way to switch out the VLAN ID from VLAN1 to VLAN10 without impacting the connectivity of the end users? No. First, you must remove the addressing from VLAN 1 before you could put that same addressing on VLAN 10 (interfaces cannot have the same or overlapping addressing). Next, if that address is your gateway, then you will ...


7

The command show interface should be showing you the information you are looking for. router#show ver | i 29 Cisco IOS Software, C2900 Software (C2900-UNIVERSALK9-M), Version 15.3(2)T, RELEASE SOFTWARE (fc3) router#show int | i Giga.*up|Duplex GigabitEthernet0/0 is up, line protocol is up Full Duplex, 100Mbps, media type is RJ45 GigabitEthernet1/0 is up, ...


7

Can one IP address be assigned to more then one device or interface? In which situations may this happen? If you actually stopped to think this through, clearly this can happen. All you need to consider is all the consumer/CPE devices that default their management interfaces to an IP address something like 192.168.1.1. Generally speaking, in a single ...


7

The document to which you link claims a specific IOS version. It may be incorrect; that would not be unusual in Cisco documentation. In reality, having tested this on several IOS 15.X versions, you do not specify a prefix length on a link-local address since it is implicit for the link local address, as you saw in your CLI help (ipv6 address ? shows X:X:X:X:...


7

Super simple answer... It tells the computer what range of addresses it can talk to before sending the traffic to the gateway to decide where it goes next. The traffic in that range never goes to the gateway. Only traffic not in that range because the computer can't "talk" to anyone but the gateway outside its subnet range. Little more details... If your ...


7

The details of this are highly dependent on the hardware, but your description is correct: for many years now it is normally the network interface card which discards the frames which don't match the MAC address. This is an improvement from the old days, where every frame would interrupt the CPU which had to do this task. In practice, every NIC can also be ...


6

You can do this with time-based ACL's when talking about ports, or with EEM when talking about interfaces: interface wlan0 ip address 10.1.1.1 255.255.255.0 ip access-group 101 in access-list 101 permit tcp 10.1.1.0 0.0.0.255 172.16.1.0 0.0.0.255 eq telnet time-range EVERYOTHERDAY time-range EVERYOTHERDAY periodic Monday Wednesday Friday ...


6

The "input errors" counter will increment whenever the interface receives a frame with any sort of input error, which includes CRC among other types of errors. Each frame is only counted once, no matter how many types of specific errors it contains. You can see an example of this if you check this recent question which also has input errors.


6

The router uses the IP address and mask configured on an interface to determine what network is attached to that interface. That network and mask then become part of the routing table as a directly connected network. There are three ways a router learns about networks: Directly connected networks Statically configured networks Networks learned through a ...


6

You can change to the SFP interface. Under the interface configuration, configure: media-type sfp To change back to the copper interface: media-type rj45


6

IP addresses are assigned to interfaces, either physical or virtual. For example, for a physical interface, such as a NIC, or a virtual interface, such as a loopback or SVI. Some people think IP addresses are assigned to hosts, but they are assigned to the interfaces of hosts, and a host can have multiple interfaces, each having an IP address (maybe more ...


6

Tim, you are trying very hard to map abstract concepts to real life hardware and software. They don't map exactly, so you always will have things that don't fit. Software is modularized for ease of coding and troubleshooting, but the divisions between modules don't line up with the concept of network layers. When we talk about software (or hardware) ...


6

As Ricky Beam has already written, even though Serial connections might not be common where you live, that doesn't mean they don't exist. Over 90% of the connections we have in Europe use either Ethernet or xDSL. But in countries like Philippines, Nigeria and Cameroon, we have a lot of Serial connections. In the end i guess it depends a lot upon where you ...


5

See this page, table 4-6: http://www.cisco.com/en/US/docs/internetworking/troubleshooting/guide/tr1904.html Description of input errors from that page: Includes runts, giants, no buffer, CRC, frame, overrun, and ignored counts. Other input-related errors can also cause the input error count to be increased, and some datagrams may have more than one error; ...


5

Am I missing some obvious crucial piece to getting this working as I had expected? You musn't confuse the latency of traffic destined to the switch with the latency through the switch. When you ping a VLAN interface on a switch, you are quite often hitting the CPU/Control plane, which in the case of most enterprise-grade switches, is not a very powerful ...


5

You're not getting adequate signal for the receiver: -22 when it wants at least -19.5 dBm. Could be a bad/dirty connector, fiber trouble, etc. My immediate suspicion is, however, the bone-simple one. I notice you are using a 1000Base-2BX10-D - is the other end also a 1000Base-2BX10-D, or is is it a 1000Base-2BX10-U? The two types must be used in pairs, one ...


5

It is the address on the interface which responds back to with ICMP timeout. Which, by default, would be the interface closest to the source.


5

You forget that routers can have virtual interfaces. For example, you can create GigbitEthernet0/0.10. You can have many, many different VLANs, each with its own network, on virtual interfaces of a single physical interface. Routers only need to terminate the layer-2 LANs. It is the LANs that really need a lot of interfaces, so you use switches for the LAN ...


5

I don't think this is possible. A broadcast storm from a bridge loop will effectively bring down much/all of your network (depending on bandwidth) but doing some permanent damage to the hardware is hardly imaginable unless cooling is barely working. Exhausting TBW on an SSD is also hardly likely - maybe with packet capture and a ring buffer... Could you ...


5

You're right: you can have unnumbered point-to-point interfaces, for the reason you gave. Have a read of this explanation of unnumbered interfaces work in Cisco routers. We normally do number interfaces for the convenience of monitoring. [EDIT] Ethernet interfaces, which are inherently multipoint interfaces, always get numbered. The two-host ethernet ...


5

I guess you're asking about JunOS, the Operating System of Juniper for their hardware. ge means Gigabit Ethernet. This a list of ethernet interfaces and names used in JunOS: ae— Aggregated Ethernet interface. et— 100-Gigabit Ethernet interfaces. fe— Fast Ethernet interface. ge— Gigabit Ethernet interface. xe— 10-Gigabit Ethernet interface. For a ...


5

You can simply create access lists to restrict traffic, and place those access lists on the VLAN interfaces. For example an ACL to prevent traffic from 10.11.12.0/24 to 10.11.13.0/24 can be created and placed on the VLAN interface for the 10.11.12.0 network: ip access-list 12 deny 10.11.13.0 0.0.0.255 ip access-list 12 permit any ! interface VLAN 12 ip ...


5

Loopback interfaces are virtual interfaces that are considered directly connected interfaces. Your Loopback0 interface is defined with a /32 network, which, by definition, is a local route. How you are seeing it when you show the routes is how the /32 is reported. If you had addressed it with a longer mask, you would also get a Local route (the /32 address). ...


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