Questions tagged [ipv4]

For questions about Internet Protocol version 4 (IPv4); as specified in RFC791.

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9
votes
5answers
8k views

Asymetric routing - causes and effects?

It happens that I run across customers who have what I define as an "asymetric routing" in their networks. Simply said, they have two gateways on the same IP subnet. The clients are configured to ...
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7answers
10k views

Subnetting a IPv4 /24 into 7 equally large subnets

I wrote a test a few days ago and wasn't able to solve one task in there: Create 7 Subnets in the 192.168.10.0/24 Net The subnets should be equally large. The address range must be completely ...
9
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4answers
53k views

How to find a list of devices connected to my network (IP's and MACs)

I am trying to get a list of the devices that are connected to my Cisco (Catalyst 2960) switch. Preferably through SNMP. Here is what I've already done: I was able to retrieve the ARP table from the ...
4
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3answers
3k views

When is /31 recommended over /30 in P2P links? [duplicate]

For your average enterprise network, what are the pros and cons for using a /31 mask on point-to-point links with private addressing over the generally accepted practice of using /30? There's really ...
16
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4answers
52k views

Bad Mask for IP Address Error

I'm not too clear on subnetting rules and experienced an error when I tried to assign 148.26.1.176/28 to an interface on my Cisco router. Can someone please explain why it was not allowing me to ...
3
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2answers
797 views

What can I do about network traffic with uknown source and destination?

I am getting more than 60% of this traffic in my network. Source Ethernet Address (6 bytes) 00:00:00:00:00:00 (XEROX CORPORATION) Destination Ethernet Address (6 bytes) 00:...
10
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2answers
2k views

Does SCTP work over the Internet?

I am working on an application that would be able to take advantage of the multi-streaming features of SCTP. Does SCTP work across the Internet? Is it supported by ISP's routers and consumer routers ...
6
votes
2answers
2k views

How do the Application, Presentation and Session layers of the OSI model map to TCP/IP's Application Layer and vice versa?

I need to map TCP/IP protocols to the OSI model for some university test revision I am doing. I was wondering if it is generally acceptable to assume any OSI Level 7, 6 and 5 protocol will be ...
13
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4answers
5k views

/31 Point-to-point bitmasks

When is it appropriate to use a /31 network in production, and is using them considered good practice? On a point-to-point link, broadcasts shouldn't be required, so is there any compelling case for ...
16
votes
2answers
7k views

IPv4 Address Space Planning Best Practices

A recent question from Craig Constantine pertained to IPv6, but many people are not on the leading edge with IPv6 yet and are still responsible for new or improved IPv4 deployments. I would like to ...
9
votes
2answers
2k views

Finding the IP of a MAC Address

Is there a way to derive the IP of a device from their MAC address on a Cisco device? Assume you are not on a local segment where ping sweeping / arp are possible, instead you are remote and there ...
10
votes
3answers
731 views

Circular BGP propagation

This one is a difficult to describe, it's hypothetical because I'm learning about routing and right now I'm focused on BGP. Let's say my ASN is 65000, and I announce 192.0.2.0/24. My peer, AS 65001 ...
3
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1answer
3k views

UDP Message Length Field and Pseudo Header

I'm learning some tcp/ip basics, and am having trouble understanding the Message Length field in UDP. In my book, it says that the Message Length represents the UDP header and data in octets, and ...
13
votes
3answers
2k views

VLAN and subnet relationship

Many have pointed out that a VLAN can hold one or more subnets. If your default gateway for this subnet is on a router or a L3 switch then how could there be more than one default gateway in a VLAN ...
37
votes
13answers
60k views

Difference between Subnet and VLAN?

You often hear the terms Subnet and VLAN used interchangeably. With the ubiquitous nature of IP these days, when are the two not considered roughly the same from a high-level, understanding that ...
13
votes
4answers
9k views

What is the use of wild card masks vs normal masks

I've always wondered what the use of wild card masks was. When I learned about them in college I wondered what the use was, we saw that you could separate subnets by for instance even and uneven IPs. ...
12
votes
4answers
2k views

How can I formulate the communication latency in TCP/IP?

I have difficulty in deriving a mathematical model/equation to estimate the round trip latency between two nodes communicating using TCP/IP. The nodes are exchanging data based on HTTP protocol. In ...
37
votes
8answers
29k views

How would a router with /32 WAN subnet mask communicate with the rest of the Internet?

I'm studying networking and one of the most basic things I've been told countless times is that computers can't communicate outside of their own subnet. On the other hand, by looking at some ADSL ...
5
votes
4answers
1k views

IP prefixes by state (geolocation) [closed]

I've been given a task of creating several filters to block outside traffic by geolocation. In the list of the places that need to be blocked there are several countries (e.g. China and India) and 5 ...
11
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2answers
3k views

Why don't iperf, scamper and path MTU discovery packet captures agree on the path's MTU?

Let's do some path MTU discovery between two Debian hosts separated by a Debian router that runs Shorewall-generated iptables rules. Each of the two hosts uses a single Ethernet link while the router ...
10
votes
4answers
1k views

Migration from IPv4 to IPv6 strategies

As everyone is aware we are out of IPv4 addresses and soon (if not already) we shall be moving on to IPv6. What are some good strategies and practices to migrate a complete IPv4 network onto IPv6?

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