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3

The maximum size of an IPv4 packet is 65,535 because the Total Length field is a 16-bit unsigned integer, which has a possible 65,536 values (from 0 to 65,535). The maximum payload is 65,515 only if the header is 20. If the header is 60, then you must subtract 40 from that because the total packet size cannot exceed 65,535. IPv6 does it differently, using ...


5

First, if you are using broadcast and network classes then you are still stuck in the last century. Network classes are dead. Broadcasts interrupt every host on the LAN (routers, printers, all PCs, etc.), including those not interested in the broadcast. Many companies now will reject applications that use broadcast because it interrupts every host, and it ...


0

Broadcasts are always received by every NIC and passed to the network stack, where they are either dropped or processed further. There are different types of broadcasts: IP limited broadcast (255.255.255.255) - this is propagated to all nodes inside the broadcast domain and processed by each NIC and IP stack IP directed broadcast (192.168.{1|2}.255) - this ...


1

A broadcast must be inspected by the network stack in every host to see if the broadcast is meant for that host. The layer-2 broadcast is the same for every frame, regardless of the network, so layer-2 will pass the broadcast up to layer-3 in the network stack. The layer-3 (IP) will look at the destination address and see that it is not meant for that host, ...


1

From my understanding of your comment: I'm trying to do split tunneling, I want a list of ranges not being routed through the tunnel, so I need a list of routes that doesn't match with these ranges. you really don't need this list. Routing works primarily by selecting the more specific route first. So in a split tunneling scheme: you have a ...


4

We can subnet Class B IP address. For example, Class B IP address is 130.168.0.0. We allocate organization with 130.168.0.0/20 block of Class B IP address (32 subnetworks). So ISP router will add just one entry for 130.168.0.0/20. That is classless routing. Classful routing means that the entire Class B network can only be used by the domain (company) ...


2

Must be zero (MBZ) is a standard convention in networking, and frequently in API design for things that have no current use but might do in the future. It is because it has no meaning that it must be 0. You might think that doesn't make much sense. Howevr, suppose I invent IPv4+ (unlikely), and persuade IANA to allocate me that bit (fantastically unlikely). ...


2

The IPv4 header is defined in RFC 791 Clause 3.1. Bit 0 in the flags field is reserved and "must be zero". It's also called the Evil Bit and all hell will break loose if it's ever set to 1. Currently-assigned values are defined as follows: 0x0 If the bit is set to 0, the packet has no evil intent. Hosts, network elements, etc., SHOULD ...


0

No, NAT doesn't need to have a private IP. You can also NAT a private IP address to another private IP address.


0

Most often, a NAT device is modeled as a router, using IP addresses for its (L3) interfaces. However, NA(P)T can also be done on any suitable device that the traffic to be translated runs through, like a bridge/switch, without using any IP address for itself.


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