Questions tagged [ip-forwarding-table]
For questions involving the IPv4 or IPv6 Forwarding Information Base (FIB).
36 questions
3
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2
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Time taken to complete a routing table update and possible interruption
I am wondering if a routing/forwarding table update at a switching node (e.x., a switch or layer-3 router) can cause momentary packet drop or increased delay for a data stream that will traverse this ...
- 35
2
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5
answers
2k
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How is an IP packet sent to the gateway?
This is some route command output sample:
$ route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 192.168.240.1 0.0.0.0 ...
- 299
0
votes
1
answer
182
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Find best route in route table using sorting [closed]
I am trying to implement a forwarding algorithm by myself with ARP, ICMP and the forwarding algorithms. Given the routing table:
typedef struct route_table_entry {
uint32_t prefix;
uint32_t ...
- 101
1
vote
2
answers
2k
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Internet Scale Routing Table Size
In the link below, it is said that there are near one million prefixes for IPv4.
https://bgp.he.net/report/netstats
I want to know that it is a must for ISP routers to cache all these million IPv4 ...
- 561
1
vote
1
answer
150
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Route advertisement and FIB programming
Que1. Assuming bgp is running on a network device, will the route advertisement and FIB programming(basically populating entries in hardware) occur in parallel?
Or does it occur sequentially, meaning, ...
- 905
0
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2
answers
720
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What are the differences between packet forwarding and network address translation in layer 3?
What are the differences between packet forwarding and network address translation in layer 3?
Is packet forwarding done by a router between two networks that use
public IP addresses?
Is network ...
- 1,565
2
votes
1
answer
246
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Two channels between two switches
Is there a way to provide two physically diverse channels between two switches? I'm using two Cisco Catalysis 3560s, and I want to have two separate channels between them, with different access ...
- 145
1
vote
1
answer
328
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Reach IP in Parent Network [closed]
We have a router (Router 2) inside a network (Router 1) with a client (Client in Router 2) that needs to make a TCP connection to a client in router 1. We only have access to configure Router 2 and ...
- 111
14
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3
answers
26k
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What is the difference between routing table and forwarding table?
What is the difference between a routing table and a forwarding table?
- 385
0
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1
answer
133
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Sys Routing Table Router: Destination IP, Gateway IP and Public IP are different, something unusual? [closed]
I am currently studying my home network router Sys Routing Table and attempting to resolve WHY my Public IP (assigned by my ISP), Gateway IP (WAN) and Destination Network (WAN) are all different.
I ...
- 103
2
votes
1
answer
353
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Deploying Dijkstra's Algorithm in a Fat Tree Topology!
I am trying to deploy Dijkstra's Algorithm for finding the shortest path between switches in a balanced fat-tree topology. The problem is that I do not know what values/unit of weight should be in ...
- 21
5
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1
answer
2k
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Switch FIB and router FIB
Forwarding Information Base (FIB) also called Forwarding Table or Mac Table according to wikipedia.
I first explain my understanding of the FIB in both Switch and Router. Does not hesitate to correct ...
- 425
1
vote
1
answer
458
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Why is Next-hop address the same with Interface address in forwarding table?
I read about TCP/IP Illustrated, Volume 1: The Protocols (2nd Edition) 5.4.3.1 Direct Delivery, this chapter illustrate the direct delivery like below:
But what confuse me is the forwarding table of S:...
- 145
1
vote
2
answers
3k
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Forwarding tables in hosts [closed]
I'm an engineering student studying networking from Kurose's A Top Down Approach. I got stuck on an exercise from chapter 5 (link layer) and wanted to fill in the gaps in my knowledge.
The exercise ...
- 113
3
votes
3
answers
2k
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Forwarding to multiple output ports using SDN
Using switches that support OpenFlow, is it possible to forward packets for specific flows to multiple outgoing ports, so that each port receives a copy of the packet (similar to multicasting scenario,...
- 151
1
vote
1
answer
875
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Flat vs Hierarchical FIB
I've been reading about FIB and tried to understand the design,
I read that FIB and RIB have one-to-one correlation.
1.What does it mean they have one-to-one correlation?
2.In my understanding - ...
- 11
1
vote
2
answers
534
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Ping issue: connect a switch into another switch's vlan port
I have a Cisco 2960-X switch and a Cisco SG-300 switch. I created VLANs on 2960-X switch (e.g. VLAN 10 with ports 1-5 and VLAN 20 with ports 6-10) and allow DHCP for each VLAN.
Now, laptop 10.10.1.2 ...
- 271
0
votes
1
answer
2k
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Port forwarding and dynamic IP address [closed]
I have a basic confusion about how port forwarding works with DHCP assigned IP addresses.
If I set up port forwarding on a raspberry pi using its internal IP address and then set up dyndns so that ...
- 111
1
vote
1
answer
112
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Which sources of information are used to forward packets?
I am trying to better understand how routing works in practice.
Which sources of information (can) go into the forwarding decision that a router makes? I have learned that BGP Updates from ...
- 35
1
vote
2
answers
857
views
Determining next hop adress in packet forwarding by forwarding table (IPv4)
Say that we have a router with the follwing forwarding table
--------------------------------------------------
| Destination | Next hop | Flags |
-------------------------------------...
2
votes
1
answer
158
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The meaning of routing table lookup at a line rate
When it is said: Routing table lookup in a line rate, why is line rate important when the router still needs to perform a linear search in the size of routing table? Is there a relationship between ...
- 411
2
votes
2
answers
481
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Does a router that connects to multiple networks, has a network card and forwarding table for each connection?
Say we have a router that connects to other routers and they connect to lan networks, does that router have a network card for each router it connects with but a single forwarding table for all? or ...
- 123
1
vote
1
answer
68
views
Switch: Misbehaving Client
Consider a switch with an empty forwarding table. Connected clients are
* A (Port 1)
* B (Port 2)
* C (Port 3)
A wants to send a package P to C. When the switch receives this package, the switch ...
- 113
2
votes
4
answers
584
views
Is Longest Prefix Matching(LPM) Done in Data or Control Plane?
I have a strong confusion on this whether LPM is done in Data or Control Plane.
My thoughts on this is as follows if its in data plane, we will have to do it for every packet hence we will have a ...
- 123
2
votes
2
answers
3k
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Cisco 2851 Static NAT - Similar Static Entry Already Exists
I have a Cisco 2851 with NAT configured as so:
ip nat inside source list 111 interface GigabitEthernet0/1 overload
ip nat inside source static 192.168.16.16 64.xxx.xxx.233
ip nat inside source static ...
- 131
1
vote
1
answer
126
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Which fields in the IPv6 header are checked during an IP lookup?
I'll consider IPv6 headers for this question.
I assume that the simplest IP lookup scheme implementation would just look at the 'Destination Address' field in the IP header of an incoming IP packet.
...
- 169
3
votes
2
answers
2k
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OSPF, BGP & Forwarding tables
I'm little bit confusing about the flow of things that happen during a voyage of packet in the internet.
my basic question is : What is the connection between OSPF and forwarding tables?
Suppose ...
- 283
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vote
3
answers
1k
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STP, Distance vectors, LS and ECMP confusing
I currently taking a computer networking course and there are some terms that really confusing me and i can't find the "connection" between them.
Suppose I have a network with hosts and routers, ...
- 283
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vote
0
answers
571
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vMX L3 MPLS VPN routes not in forwarding table
I'm new to juniper technology and I'm trying to set up mpls vpn on vMX.
Not sure if I'm missing something in configuration or if this is some kind of bug in vMX or if this is not supported on vMX.
As ...
- 11
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vote
1
answer
1k
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Basic example of forwarding tables
This is my network. The forwarding tables I provide them bellow. I am able to establish the connection between Office1 and R1 but I am not able to connect with R2, as for a reason I do not know, all ...
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3
votes
1
answer
1k
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Routing and Forwarding Decisions
We need to build a routing table, based on routes from neighbors..
Route A receives three routes from different Routing Process:
EIGRP - 192.168.100.0/26
OSPF - 192.168.100.0/19
RIP - 192.168.100....
0
votes
2
answers
740
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Ip forwarding & routing table advanced example! [closed]
I'm have a big question regarding IP forwarding. The current situation is like this:
I want to send a packet from the client to the server, between them I have two routers, Router1 and Router 2. ...
- 95
1
vote
1
answer
76
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Pair two communicating processes separated by two firewalls
Suppose you have 4 processes inside one network (no firewalls) and you see (hostnames A,B,C,D):
From A:1 -> C:3
From B:2 -> D:4
Therefore you know A is communicating with C and B with D.
Now ...
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1
vote
1
answer
12k
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Why cant i NAT to a local network address on my UBNT edgerouter
I am trying to set up a very simple network.
I have an Ubiquiti Edgerouter on 192.168.1.1 with eth0 as WAN port.
I also have an Ubiquiti Rocket m5 on 192.168.1.2, both the router and the Rocket have ...
- 113
1
vote
1
answer
5k
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Configure DNS Table on Sonic Wall TZ205
I just installed a TZ-205 on our company network and I can not seem to find where I would add to a DNS table. On our Linksys LRT224 there is a option to add a domain name and an associated IP. Does ...
- 147
5
votes
2
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526
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