Questions tagged [ipv4]
For questions about Internet Protocol version 4 (IPv4); as specified in RFC791.
889
questions
137
votes
6
answers
865k
views
How do you calculate the prefix, network, subnet, and host numbers?
Example:
IP: 128.42.5.4
In binary: 10000000 00101010 00000101 00000100
Subnet: 255.255.248.0
How could you determine the prefix, network, subnet, and host numbers?
- 1,459
5
votes
1
answer
923
views
Remote Port Forwarding Cisco
I have a Cisco3900 called router A (192.168.100.1), which is interconnected to another router B (192.168.100.2). I want to access my server C 220.221.x.x (which is on internet).
Router A (192.168.100....
- 51
2
votes
1
answer
850
views
Do routers validate the IP packet length?
Do routers verify the actual IP packet size with that mentioned in the packet?
- 21
1
vote
1
answer
841
views
Cisco Prime Infrastructure 2.0 : IP Type - Not Detected
I have a Cisco Prime Infrastructure server which has fully discovered all my devices on my network.
But when I go to the "Clients & Users" tab (the new name of the old "User Tracking" feature), a ...
- 787
9
votes
3
answers
65k
views
Maximum IPv4 header size
I know the IP header length is a minimum of 20 bytes and a maximum of 60 bytes. But why? Why is the IP header length limited to 60 bytes? Is there anybody here that can explain it to me? Thank you.
- 151
1
vote
1
answer
3k
views
What is this UDP 5002 broadcast?
I hope this is an appropriate place to ask this.
I'm confused because it's a broadcast at Layer 2 but it's UDP inside a VLAN with a destination to a unicast address (Y.Y.Y.Y).
I was just wondering ...
- 153
5
votes
1
answer
2k
views
VRRP-Extended - can't ping
I have 2 brocade switches running vrrp-extended for a specific vlan. Connected to these 2 is an access switch with the default route set to the vrrp-extended virtual ip address.
The problem is that ...
- 1,388
3
votes
1
answer
443
views
Internet Protocol. Source Routing. RFC 791. Are the addresses in the Source Routing option 1-indexed?
I was reading pages 18-21 in RFC 791 about the Internet Protocol and in the sections on Loose Source and Record Route (LSRR), and Strict Source and Record Route (SSRR), and Record Route (RR) it says ...
- 133
5
votes
1
answer
546
views
NAT translation mystery
We have an mail server and its private address is translated to public on a Cisco router. We've mapped it one-to-one using this command:
ip nat inside source static 192.168.7.7 198.51.100.7 route-map ...
- 837
2
votes
3
answers
5k
views
Reliablity vs unreliable service at IP and Link Layer
I am taking about the 5 layer model. It is well documented that TCP is a reliable service and IP is best-effort delivery and hence unreliable (ref RFC 792 - TCP). Also, the data link layer is '...
- 123
8
votes
1
answer
798
views
will ping work if there are 500 routers between pc1 and pc2?
As the ttl is 255 maximum for ipv4 on cisco routers, will ping work if there are 500 routers between pc1 and pc2?
- 89
17
votes
4
answers
73k
views
Confusing A, B, C network classes
I'm studying IPv4 addresses and came across this whole thing about classful addressing. I get the idea behind it, bit there is something I find confusing:
There are two "ABC" ranges:
First one:
A: ...
- 671
8
votes
2
answers
3k
views
How is the IP prefix passed to the router?
First some background information on what I already know:
An IPv4 address is a 32 bit address that identifies a node in a network. An IP address will have an IP prefix which determines the "Network" ...
- 283
5
votes
2
answers
235
views
Locating a single IPv6 or IPv4 routable prefix at multiple data centers
Academic question (at the moment):
Is it possible to advertise BGP routes to a given prefix (IPv6 and/or IPv4) from multiple different physical data centers?
I guess this is multi-homing, but ...
- 151
1
vote
2
answers
7k
views
Why is the target IP address always my default gateway?
I am currently researching ARP packets using Wireshark and have found that when I ping a new computer asking for the MAC address that corresponds with the known IP address, my target IP address in my ...
- 303
1
vote
1
answer
401
views
Basic question about private IP addressing -Class B
Below I will translate from decimal to binary just for the second octet
The theory says the IP range is:
172.16.0.0/12 with addresses ranging between 172.16.0.0-172.31.255.2555
that translates to:
...
- 415
10
votes
3
answers
7k
views
How HTTP is converted to TCP and then how TCP converted to IP?
I know that in Internet Protocol Stack there are actually three layer. They are Application, Internet and Transport. Let's say HTTP in Application layer will be converted to TCP in Transport layer and ...
- 201
4
votes
3
answers
3k
views
Is there any recommended range for ip router id
Generally a router id will be set to highest loopback address if present or the highest ip address of physical interface. But most vendors provide a way to configure a specific value example:- " ip ...
- 1,124
4
votes
2
answers
1k
views
Path MTU discovery and retransmission
I'm reading about IP at the moment and one thing I haven't been able to comprehend very well, is the retransmit situation for IP packets with DF set.
In this situation, I assume the following happens ...
- 327
14
votes
2
answers
11k
views
What is a non-portable IPv4 address block?
For example, a Whois query for 4.4.4.0 says:
ADDRESSES WITHIN THIS BLOCK ARE NON-PORTABLE
Does the owner simply declare the block or a subnet are not up for sale? Or does non-portable have a ...
- 860
1
vote
2
answers
2k
views
How can i make Public IP of this ISP given information?
I have a Draytek Vigor 2920, Juniper SRX 210 router, and Cisco SC300-10 switch. I am very confused; how can I set it up so that I have a public IP address on my Dell R310?
1 - My ISP, Telenet from ...
- 115
3
votes
4
answers
7k
views
When a ping is lost, what happens?
Suppose that the message you are sending does not reach the destination, such as a ping. Is the content of that message protected? How is a retransmission accomplished?
- 303
9
votes
2
answers
3k
views
Differences and functions of type codes 0800 and 0806
What are the primary differences and functions (or applications) of type codes 0800 and 0806?
Through my own research, I found the 0800 was related to the 0800 to the IP/Layer 3 of the OSI model.
...
- 303
43
votes
3
answers
63k
views
Why 192.168.*.* for local addresses? [closed]
The standard I've seen so far is to use 192.168.*.* IP addresses for devices on the local network.
Why this combination? If it were me, I would have chosen something simpler, like 1.0.*.*. What's the ...
user3878
8
votes
1
answer
8k
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 ...
- 860
1
vote
2
answers
23k
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.
...
- 1,611
3
votes
1
answer
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 ...
- 133
5
votes
2
answers
3k
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 ...
- 153
0
votes
1
answer
890
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 ...
- 135
3
votes
2
answers
218
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 ...
- 275
-1
votes
1
answer
338
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 ...
- 11
4
votes
2
answers
825
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.
- 43
2
votes
3
answers
847
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 ...
- 263
16
votes
3
answers
12k
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:
...
- 313
12
votes
3
answers
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 ...
- 223
9
votes
2
answers
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. ...
- 685
3
votes
5
answers
5k
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, ...
- 31
262
votes
6
answers
496k
views
1
vote
3
answers
173
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 ...
ravigs
5
votes
2
answers
523
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 ...
- 53
4
votes
1
answer
2k
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 ...
- 1,015
3
votes
1
answer
735
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 ...
- 463
7
votes
2
answers
3k
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 - ...
- 237
5
votes
2
answers
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 ...
- 463
5
votes
1
answer
1k
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?
- 127
21
votes
4
answers
25k
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 ...
- 313
56
votes
10
answers
101k
views
Reason for both a MAC and an IP address
If my computer has an IP address,why does it need a MAC address?
- 837
4
votes
2
answers
591
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.
user190627
13
votes
3
answers
36k
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 ...
- 517
7
votes
2
answers
13k
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 ...
- 193