6
votes
Accepted
Does the IP header have a "Padding" field?
Padding is only used if there are options that are not an even 32 bits. The whole header must be divisible by 32 bits. RFC 791, Internet Protocol has the official header:
3.1.
Internet Header Format
...
- 97.7k
5
votes
What does 'moving packets away from the source' in RPF means?
RPF is one tool in your toolbox to help keep your network safe. RPF is used to verify that packets are coming from the direction of a reachable source. This helps to prevent malicious packets from ...
- 97.7k
4
votes
Does the MSS (Maximum Segment Size) prevent IP Fragmentation in all cases?
Does the MSS (Maximum Segment Size) prevents IP Fragmentation in all
cases?
No. What prevents in-path IP fragmentation is to use the IPv4 DF flag, or use IPv6. If an IPv4 packet does not have the DF ...
- 97.7k
4
votes
How to obtain a range of IPv4 or IPv6 addresses as an individual
IP addresses can be either directly assigned by a RIR or allocated by the provider who provides internet connectivity. Precise policies vary by RIR but generally for a direct allocation you need to ...
- 12.8k
4
votes
Accepted
Could we use an IP address in our network that does not fall into the RFC 1918 range?
You could, but you shouldn't. If you do so, the real devices and services using that IP range become unreachable.
I've seen a number of customers make this mistake (sometimes intentional, sometimes ...
- 16.6k
4
votes
Are the IP protocols contained in the Protocol Field in IPv4 header, chronologically assigned by date of creation?
Are the IP protocols contained in the Protocol Field in IPv4 header,
chronologically assigned by date of creation?
Not necessarily, but also remember that the first RFC for IPv6 was published in 1995,...
- 97.7k
4
votes
Not able to ping device with different subnet on gateway and ip adress
The gateway address must be in the same subnet as the interface address. So your device is misconfigured.
- 66k
4
votes
Accepted
How does subnetting solve the problem of IPv4 address shortage?
Consider a network that needs 300 addresses. A class C block is too small, so they would get a class B, even though they're not using over 65,000 addresses. If you have 10 networks, that's a lot of ...
- 66k
4
votes
How did ATM switches that were implemented in a core of IP network improve QoS and higher data rate?
ATM (which is all but obsolete today) provided classes of service that guaranteed bandwidth resources. That feature has been replaced by classes of service in IP (using DSCP markings) that can be ...
- 66k
3
votes
Are the IP protocols contained in the Protocol Field in IPv4 header, chronologically assigned by date of creation?
Nope, they are definitely not numbered in chronological order of creation/adoption because some of the IPv6 ones were created much later (at least about 4-6 years or so) than some of the higher ...
- 1,568
3
votes
Why do we need DNS?
You can do calculations on IP addresses, not on domain names. This allows you to do subnetting, aggregation, route comparison, and many more things.
These functions are needed to do route selection, ...
- 16.6k
3
votes
Accepted
The relationship between IP address and AS number
You're mixing up two things here: ownership of the IP-range and the right to advertise IP addresses. Ownership of IP addresses has nothing to do with ASN's. The owner of an IP range may allow one or ...
- 16.6k
3
votes
How does subnetting solve the problem of IPv4 address shortage?
Likely that should say subnetting of classful networks solves the problem of IPv4 address shortage. Classful networking is long dead. It died in 1993 with the introduction of CIDR. Please leave it ...
- 79.7k
3
votes
Accepted
Why Linux answers ARP requests for IPs that belong to different network interfaces?
0 - (default) The kernel can respond to arp requests with addresses
from other interfaces. This may seem wrong but it usually makes sense,
because it increases the chance of successful communication. ...
- 31.1k
2
votes
How does Network Layer behave when client received a unicast DHCP offer?
A host might not be able to accept a unicast DHCP offer when it doesn't have an address configured. If so it shouldn't claim that it can:
A client that cannot receive unicast IP datagrams until its ...
- 1,558
2
votes
How CIDR helped to slow down routing table growth?
Im writing a new answer because on reflection I was initially incorrect. CIDR did reduce the routing table size.
In theory, classful routing has a maximum of about 2.1 million possible networks (all ...
- 66k
2
votes
Can you send data in LAN without an IP?
So Can you commuincate within a LAN, with help of MAC Addresses only ?
Yes, absolutely. That's actually what IP does, it uses the data link layer (L2) as transport vehicle, with the underlying layer ...
- 79.7k
2
votes
Usage of Flow label in IPv6 header?
RFC 6294 "Survey of Proposed Use Cases for the IPv6 Flow Label" is definitely the answer to the question. One quote:
There was considerable debate in the IETF about the very purpose of the ...
- 121
2
votes
Maximum packet size Ethernet Frame and IP packet
In short the exact definition of fragmentation is part of the answer.
First, as some have answered, these are from specifications of ethernet and IP (IPv4). Since there are other Layer 2 (Data Link ...
- 121
2
votes
Accepted
Can you send data in LAN without an IP?
Yes, Apparently I figured it out myself... so, if you craft your own packets, you can.
I achieved this by using Python's Scapy library. and crafted Ethernet packets and successfully communicated over ...
- 51
2
votes
Are encapsulation and decapsulation really happening inside an operating system?
Encapsulation (prepending of lower-layer header) and decapsulation (removal of that header) happen within each layer.
The "payload" (SDU data) to send is passed from the higher layer, ...
- 79.7k
2
votes
How to correctly setup a DHCP server in the following network?
There is no 'correct' way. Basically, you can either setup or connect a DHCP server to each subnet, or set up a central DHCP server and configure relays on the routers (or switches). Both variants can ...
- 79.7k
2
votes
Accepted
What does 'moving packets away from the source' in RPF means?
With unicast traffic you have a single destination, so you know exactly where you're going. In case of multicast you can go to 100 receivers, or 10, or 0. Receivers can connect as you send the ...
- 1,591
1
vote
What are all the reasons for using a separate /31 subnet for a p2p link?
Routers route between subnets and each subnet needs to have a unique address/prefix. If a subnet is used for a point-to-point link only then /31 is the best choice you can make. Also common are /30 ...
- 79.7k
1
vote
ICMP error message's data for IP datagram with < 64 bits payload?
I'd venture that such a packet header would be padded with zeros (which is very much the standard procedure).
However, you'd be really hard pressed to create or even run across a practical packet with ...
- 79.7k
1
vote
How ARP works [Specific Case]?
ARP is a broadcast that does not cross a router. ARP is only used on the local LAN to get the layer-2 address from a layer-3 address. When a host sends a packet, it builds a frame for the packet. If ...
- 97.7k
1
vote
routing table What does this mean (brackets in routing table)?
The FGT1 in the first line seems to indicate a FortiGate. The values in [] brackets indicate the route's administrative distance and metric.
Fortinet documents that output rather poorly but it becomes ...
- 79.7k
1
vote
Could we use an IP address in our network that does not fall into the RFC 1918 range?
Indeed you can but you shouldn't. What happened in the past, at the beginning of the Internet, was that companies rented public C classes from IANA because it was cheap ('90s/2000's)and used that to ...
- 11
1
vote
Accepted
What does "direct-attached networks" mean?
That is the network to which your host is directly attached. If you are directly attached to an ethernet network, then the MTU is 1500 octets. Different data-link protocols have different MTUs.
- 97.7k
1
vote
Can you send data in LAN without an IP?
Of course, if you create your own communication protocols within the local network, it is only possible to communicate with the MAC address. however, this is not possible when it comes to messaging ...
- 161
Only top scored, non community-wiki answers of a minimum length are eligible