Questions tagged [ipv4]

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

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7
votes
1answer
7k views

Is it possible to use single MAC address for multiple IPv4 addresses?

Topology: modem with router and Ethernet LAN bridge <---> server having one NIC. Server network interface: It is capable of handling more than one IPv4 address. All addresses are within the same ...
-1
votes
2answers
21k views

How can routers forward broadcast traffic?

I was asked by an interviewer about the following question: Is there any way to make routers to forward Broadcast traffic? I said no for the above question as routers break the broadcast domain. ...
3
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1answer
4k views

standard results for gigabit ethernet iperf

I can't achieve good transfer rate through scp and I wonder if the network configuration isn't tuned up correctly. I've noticed some differences when running iperf through tcp vs udp. Are these ...
5
votes
2answers
2k views

How to reduce latency on ASA 5510 WAN link?

I have a Cisco ASA 5510 connecting our office via 2Mbit/s Internet. When Internet link fills up, latency to a well-connected host on Internet goes from 5-8 ms to 500-800 ms. With ping, it may look ...
0
votes
1answer
725 views

TCP/IP Header compression

I'm reading RFC 1144 and I'm trying to figure out how the TCP/IP header compression works. As I understand it, the sender only sends a couple of fields that are likely to be changed. If the packet ...
3
votes
2answers
212 views

group AS number for specific country ex Germany

do anyone know how to group all AS numbers for Germany (f.example). Do they have some specific attributes to build a regular expression or something like this, something like a filter for all AS ...
-1
votes
1answer
331 views

Determining the CIDR notation to provider host per subnet

The question is: Given the Network ID 41.149.210.0/24, subnet to provide 12 usable hosts per subnet. What is the new mask in CIDR notation (without the leading /)? My question is, how... and ...
4
votes
2answers
770 views

The Difference Between ACL and FPM

What's the difference between ACL and FPM? In detail, please, but in a simple, easy-to-understand way.
2
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3answers
746 views

Calculating netmask length when combing network prefixes

Say for example I combine 16 existing prefixes which have '/12' netmask length, how would I calculate the netmask length of the new address? I know how to combine 2 addresses, but not sure how to go ...
16
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3answers
11k views

mtr output with high packet loss on one hop

I'm investigating a complaint of poor performance from an end user accessing a site I help maintain. I have these two mtr outputs to the end user, the first from the site: ...
11
votes
3answers
2k views

How are the hosts in the tracert 216.81.59.173 able to use random domain names? [closed]

How are the host names in this trace route able to use random top level domains? I didn't know there was an 'Empire' or 'victory' top level domain. C:\Users\Chloe> tracert 216.81.59.173 Tracing ...
9
votes
2answers
4k views

How can hosts with public IP addresses have nodes with private IP addresses in their traceroute?

I'm doing some research on users connected to Internet via cable operators and I've seen some unusual route traces. A bit about setup: Basically user has a home router connected to a DOCSIS modem. ...
3
votes
5answers
3k views

Subnet within a subnet

What are the consequences of having a subnet within a subnet? Eg. First network is 10.0.0.0/8 and the second is 10.0.1.0/24. Thanks for everyone's replies. The original design, which is not my own, ...
214
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6answers
412k views

The slash after an IP Address - CIDR Notation

What does the "/16" means in here : "192.168.0.0/16", for example.
1
vote
3answers
170 views

Clarification about Corporate Networking Gateway

How does a gateway identify the destination PC when the response comes back to it? Suppose there is an organisation which has many computers. All these computers have a specific range of IP ...
5
votes
2answers
495 views

coexistance for the longest prefix match

For example, can 128.92.128.0/17 and 128.92.128.0/18 be contained in one forwarding table together? Or the first one must be changed to 128.92.192.0/18? Because the other half will go to the second ...
4
votes
1answer
1k views

OpenVPN, JumboFrames and the Internet

I've been doing some research in to OpenVPN, MTU, JumboFrames, ect... and want to make sure that I have this right. If I increase the MTU over 1500 to 9000 for OpenVPN when connecting to a remote ...
3
votes
1answer
676 views

CIsco ASA 5505 have to change IP address of Server due to restructure

I just went through and restructured my IP pool on vlan 1. My issue is that my Windows VPN Server is now 10.1.10.11 instead of 10.1.10.122. I statically assigned the Windows server outside of my IP ...
7
votes
2answers
2k views

Subnetting aggregation

I saw this example online . 192.168.12.0/23 applies the network mask 255.255.254.0 to the 192.168 network, starting at 192.168.12.0. This notation represents the address range 192.168.12.0 - ...
5
votes
2answers
6k views

Obtain Static IP set in DHCP on Cisco ASA

I am working with an ASA-5505. I am trying to set aside a set of 10 IP addresses. Currently I have internally 10.1.10.100 - 254 set for my current vlan -- vlan 1, and all equipment attached is ...
5
votes
1answer
982 views

IGMP snooping in iptv

Host1 wants to join Multicast group as IGMPv3 include (G,S). The same group and source Host2 send as Exclude(G,S) report. what process done in switch?
20
votes
4answers
22k views

Risks of using non-private IP addresses internally?

My company has received a large industrial machine with many networked devices on it. Unfortunately the engineer in charge has used a public IP address range on the machine. I'm in Europe. The chosen ...
36
votes
9answers
79k views

Reason for both a MAC and an IP address

If my computer has an IP address,why does it need a MAC address?
4
votes
2answers
538 views

IGMP snooping (Bridge operation)

What is Meant by RFC 4541 when it says... 4) All non-IPv4 multicast packets should continue to be flooded out to all remaining ports in the forwarding state as per normal IEEE bridging operations.
12
votes
3answers
24k views

Wifi TCP iperf throughput: 1 stream vs multiple streams?

In a WLAN iperf TCP throughput test, multiple parallel streams will give me higher throughput than 1 stream. I tried increasing the TCP window size, but I still cannot achieve the max throughput with ...
7
votes
2answers
11k views

F5 session timeouts

Our F5 load balancers run version 10.2.4. We migrated from Cisco load balancer cards on the Catalyst 6500 and used to be able to run xterm sessions to our solaris and linux servers without the ...
10
votes
1answer
4k views

Unicast RPF On the Edge

Unicast RPF is supposed to prevent source addresses that differ from what they should be to be allowed. While reading Cisco's documentation for URPF, I noticed that there are options to allow it to be ...
1
vote
3answers
2k views

IPv4 & IPv6 IPSec differences

I am an undergraduate student where I decided to develop a firmware that would eliminate the security vulnerabilities that exist within the current technologies used. such as tunneling, translation ...
14
votes
5answers
36k views

Finding IP Addresses for Social Network Sites

How do I find out a company like facebook's IP addresses. I am trying to block facebook at work and having some difficulties with HTTPs and URL blocking. Everytime I block a facebook IP more seem to ...
10
votes
5answers
6k views

Packet sizes in a TCP stream

I'm network traffic and wish to divide each TCP session into a series of requests and responses (the protocols I'm working with all work that way, like HTTP or SSL). I had a simple assumption (...
18
votes
3answers
1k views

How does multihoming work with ipv6?

What are the differences between multihoming in IPv4 versus IPv6? Can an enterprise request a provider-independent IPv6 address space from its RIR/LIR which can be advertised to multiple upstream ...
7
votes
1answer
3k views

Position of source and destination IP in an IP packet

In an Ethernet frame header, the destination MAC (DMAC) is placed before the source MAC for obvious reasons (stations accept based on DMAC). But why is not the same thing maintained for destination IP ...
14
votes
5answers
10k views

Duplicate IP Address - which one wins?

If there's a duplicate IP address, which one "wins"? First, last, flaps, neither?
12
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2answers
15k views

Directed and Limited Broadcast confusion

Let's say I am on a network 192.168.1.X and I use the below ping commands. ping 255.255.255.255 ping 192.168.1.255 Why we are calling 1st one as limited and 2nd one as directed ? In what category ...
5
votes
4answers
17k views

How many TCP/IP layers are involved when I am pinging my router and my PC?

How many TCP/IP layers are involved when I am pinging my router and my PC? My router : ping 192.168.1.1 My PC : ping 127.0.0.1 My PC : Ping 192.168.1.10 I need to know how the data is transferred ...
41
votes
1answer
4k views

Why is such a large IPv4 range assigned to localhost?

Why is so large a range of IPv4 addresses assigned to localhost, (127.0.0.0 through 127.255.255.255)?
7
votes
1answer
1k views

Establishing IP DHCP Snooping

Have establsihed a lab to test IP DHCP SNOOPING prior to implemntation. So far everything works as advertised. Given that the Uplink port of a switch must be trusted, why is it not necessary to add ...
10
votes
4answers
22k views

Using IP addresses from IP pool given by ISP

My ISP says that it can provide an optic fiber connection with a pool of 4 static IP addresses (subnet 255.255.255.248 i think). My question is that if I get that connection, 1 ip will be used for ...
6
votes
3answers
296 views

/23 PI space - breakup

a client currently has a /23 PI space where the route-object is currently managed by ISP-A we want to split the PI space into two /24's but not certain on how best to go about this. ISP-A will use ...
8
votes
1answer
2k views

Wireshark Filter - OSPF Database Description Link State ID

Within Wireshark, how would one write a display filter for the IP address of the Link State ID within an OSPF Database Description packet? The Link State ID addresses are found within the LSA Header ...
11
votes
3answers
1k views

Do today's routers prevent fake IP headers?

I know people can modify the IP headers and change source IP address, but it should be simple for network devices to detect those messages. If they don't, why is it so hard? Does it add too much ...
39
votes
4answers
22k views

How to check for a valid public IP address?

Consider a list of IP addresses as provided by the X-Forwarded-For HTTP header: 10.0.0.142 , 192.168.0.10 , 212.43.234.12 , 54.23.66.43 I would like to know which is the first publicly-accessible ...
2
votes
1answer
1k views

Portforwarding by Subdomain [closed]

I want to have multiple servers behind a single firewall and access each with a different subdomain. Currently, I am having to have each server tied to a different port (which my firewall forwards to ...
24
votes
1answer
788 views

Should IPv4 ICMP from untrusted interfaces be blocked?

Searching around I haven't been able to determine the best practice for ICMP on a firewall. For example on a Cisco ASA would it be safe and recommended to allow ICMP from any if ICMP inspection is ...
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 ...
1
vote
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
votes
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
votes
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
votes
4answers
51k 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
votes
2answers
784 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:...