12
votes
Accepted
How many IP addresses can a device or an interface possess?
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 ...
- 27.2k
12
votes
Accepted
Why do I get "% Warning: use /31 mask on non point-to-point interface cautiously" when I use a /31 subnet mask?
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 ...
- 98.8k
11
votes
Why do I need to specify a subnet mask on interface?
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 ...
- 928
10
votes
Accepted
Why do I need to specify a subnet mask on interface?
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 ...
- 98.8k
10
votes
Accepted
How not to route on a Cisco router
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) ...
- 8,826
8
votes
Accepted
Which physical interface would be used to send/receive packets intended for a loopback interface?
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 ...
8
votes
Accepted
Switching interface VLAN ID Mid-Production
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 ...
- 98.8k
7
votes
Accepted
Why is Cisco enforcing X:X:X:X::X for link-local addresses when the standard says FE80:/10?
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 ...
- 98.8k
7
votes
Why do routers have only a few interfaces?
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 ...
- 98.8k
7
votes
Accepted
What is responsible for dropping Layer 2 frames that's not addressed to it?
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 ...
- 16.2k
7
votes
Serial interfaces of router are used nowadays?
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 ...
- 1,732
6
votes
Accepted
EHWIC-1GE-SFP for Cisco 1941
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
- 98.8k
6
votes
Accepted
What's the relationship of a Router with its loopback interface in logic?
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 ...
- 98.8k
6
votes
Accepted
What can an IP address be assigned to?
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 ...
- 98.8k
6
votes
Accepted
Do the concepts of IP address and network interface not belong to the same layer?
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 ...
- 67.1k
5
votes
Accepted
Does traceroute show the IP address of the entry port? or exit port?
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.
- 98.8k
5
votes
How to know the interface utilization on a Cisco switch?
What you are looking at is the bit rate over the last five minutes. You can change the time period, but not below 30 seconds with the load-interval command.
I'm not sure what you mean by "utilization....
- 98.8k
5
votes
What is the difference between WAN and LAN ports?
A LAN is typically something completely within your own premises (your organization's campus, or building, or office suite, or your home), so it's something you build and own yourself, all the way ...
5
votes
Accepted
What it means to configure two global ipv6 address on a single interface?
IPv6 allows, and often requires, multiple addresses on the same interface. The is more difficult in IPv4, although not always impossible.
What it means is that a host configured with multiple ...
- 98.8k
5
votes
Accepted
Can a broadcast storm do physical damage to computers and networking hardware?
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 ...
- 82.7k
5
votes
Why it is neccesary to assign IP adresses to interfaces?
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 ...
- 16.2k
5
votes
Accepted
Interfaces named with `ge` represent what?
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 ...
- 4,497
5
votes
How not to route on a Cisco router
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 ...
- 98.8k
5
votes
Accepted
Urgent: how to configure different interface using same ip subnet in asa 5506?
The ASA 5506 doesn't have the switchport commands like the 5505. In routed mode, each interface is on a separate subnet, like a router.
- 67.1k
5
votes
How does a router know the MTU of a network?
Routers know because they have physical interfaces connected to the networks. Those interfaces are configured for the correct MTU.
You are mistaken about OSPF: The protocol does not exchange MTU ...
- 67.1k
5
votes
Cisco ASA 5585X Internal-Data0/1 interface errors
From Cisco tech note:
The ASA interface error counter "overrun" tracks the number of times
that a packet was received on the network interface, but there was no
available space in the interface ...
- 67.1k
5
votes
Accepted
What's the `line protocol` and `Link`?
For this particular interface, the line protocol is ethernet.
The Link Up/Down Trap is enabled message is telling you that the SNMP trap for when the link goes up or down, for whatever reason (admin ...
- 98.8k
5
votes
Relationship between full duplex and speed
Full-duplex data transmission means that data can be transmitted in both directions on a signal carrier at the same time.
That is incorrect. It means devices can transmit and receive at the same ...
- 67.1k
Only top scored, non community-wiki answers of a minimum length are eligible