Questions tagged [routing]
For questions about routing, the process of selecting to which network path traffic is sent. Consider using a more specific tag if your question is about a routing protocol like BGP or OSPF.
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NAT Overlapping
I am trying to do some networking lab. Basically, I have a network like this:
So, is it possible to configure NAT router in such way, that PC1 and PC2 can access remote HOST and each other. The ...
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Why must all areas connect to an Area 0 backbone in OSPF?
This question is a literal repost of the same question asked on The Cisco Support Community. Answers are unique to Stack Exchange.
Why is area 0 the backbone area in OSPF? Why must all other areas ...
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Is an entirely decentralised peer-to-peer network feasible? How far could it be scaled?
Most of the reading I've done about P2P networks are either about small scale simple mesh networks, where every peer can talk to another, or about high level protocols such as bittorrent, where data ...
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How does the router know how to route the packets to my terminal?
Suppose I have a network of 2 computers, each having a private network address of 192.168.1.101 and 192.106.1.102.
For my public ip address, it is 10.2.10.172.
When I make a http request to google....
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When is BGP needed?
I have a question about BGP.
When exactly is BGP needed?
I remember reading that BGP is needed for communication between autonomous systems, but is this always true?
For example, in packet tracer I ...
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Does CIDR really "do away" with IP address classes?
I am still struggling to understand to what extent CIDR really renders IP address classes obsolete. Here's what I understood so far:
It's ridiculously inefficient (and impossible, too) to assign ...
user15544
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3
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MPLS vs Encrypted VPNs - traffic security?
Why do people say a lot of times that they have two connections between two offices - the main one being over MPLS and the backup one over VPN. Why not run a VPN over MPLS too? Is MPLS secure? Can no ...
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How are MAC/IP addresses used in routing
I have to teach my sixth form about MAC Addresses and IP Addresses in a few weeks time and there are some areas I am unclear on which I am hoping some of you will be able to clarify for me. I have ...
- 131
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Dell PowerConnect 5524 VLAN routing
I have a Dell PowerConnect 5524 that I'm trying to configure.
What I want is simple routing between VLANs and the user guide is less than helpful.
On page 220, it says (or implies) that all you need ...
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How can hosts on two different VLANs communicate?
It is clear that hosts on two different VLANs can't directly communicate on a single switch, but how do they communicate to each other at all? Do they use a router? How does it work?
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VLAN-Subnets 1:1?
I often hear people saying that each VLAN is a subnet (or is associated with a subnet) but is that really true?
Assume I have 10 big offices. I will have a subnet for each office but only 2 VLANs ...
- 121
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Do all network devices need to make routing decisions, regardless of communication across networks or within a network?
From Hunt's TCP/IP Network Adminstration:
Gateways route data between networks, but all network devices, hosts as well as
gateways, must make routing decisions.
Is it correct that routing ...
- 1,505
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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 ...
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In which OSI/TCP-IP model layers do BGP, RIP protocols belong?
We know that in the OSI or TCP-IP model, the higher layer utilizes the services offered by the lower layer. For example, the data link layer uses services offered by the physical layer, network layer ...
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How is BGP "AS_SET" used?
RFC 1771 defines a path attribute type of AS_PATH as follows:
AS_PATH (Type Code 2):
AS_PATH is a well-known mandatory attribute that is composed
of a sequence of AS path segments. Each AS path ...
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How does NAT share one public IPv4 address across multiple private IPv4 addresses [closed]
I think it's a very classical question, but, thought I've have some background, I don't have enough vocabulary anymore to search and understand correctly in the Web.
Let's say I have a home network ...
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Inbound BGP load-balancing from same ISP router
I have two BGP routers for DIA with an issue with one provider in that the two links to this provider land on the same SP router. My ethernet handoffs via two separate MetroE links from another ...
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Static routes: numerical next-hop vs interface
I'm reviewing old Cisco modules, and in CCNA 2, Module 2.5.1.2, it states,
Under certain conditions, the network administrator will not want to configure the static route with an exit interface but ...
user3046
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IPv6 and online privacy and security
I am studying up on IPv6 and part of the talk was about how the machines generate or can have multiple IPv6 addresses for internal use and external use.
Does this mean that there is no longer a "...
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Does a router send frames or packets?
Perhaps it's a novice question, but does a router send/receive frames?
When I read about this subject, it seems that routers decapsulate the frame on arrival, and encapsulate the packet in a frame in ...
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Who decided the Admin Distance Values for each protocol?
OSPF has an administrative distance of 110
EIGRP has an administrative distance of 90
RIP has an administrative distance of 120
But where did 110, 90, and 120 come from?
Who or what entity decided ...
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At which layer does router operate?
I have studied from various sources that router is a layer 3 device. It does routing based on Network layer (layer 3) header, but I have a doubt.
Network address translation (NAT) is a feature of ...
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minimum hop limit for a packet where there are n routers between source and destination
I am having some confusion while calculating he minimum hop limit ...
consider following scenario:
(source)-------(R1)--------(R2)--------(destination)
Now when an IP datagram is supposed to travel ...
- 133
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What is the point of a subnet mask on a local network?
I have a question regarding subnet masks and my understanding (or misunderstanding of them).
So when a subnet mask is used, a bitwise AND is performed using the subnet mask and the IP address(es). ...
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What is nodal delay?
I keep seeing the definition of nodal processing delay as "The time it takes to process a packet in a network node (router, switch, hub, etc.), which is dependent on the speed of the device and ...
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Cisco Prefix List Won't Appear in Route Table
I have the following prefix-list configured on our router:
ip prefix-list adsvr seq 5 permit 172.30.5.241/32
ip prefix-list adsvr seq 10 permit 134.239.130.143/32
ip prefix-list adsvr seq 15 permit ...
- 203
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2
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CGN and its advantages
I have been reading about CGN. Though similar to NAT it is used by service providers to route traffic without the need for the a public IP address.
But when the packet leaves the ISP to the public ...
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What is the election process of Router ID in OSPF?
I am a little confused on the process OSPF uses to select the Router ID. Is following correct for the selection of the router ID in OSPF?
Manual configuration
Highest IP address on a loopback ...
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Why does OSPF use flooding instead of broadcasting?
In flooding, we send unicast/multicast frames to all the routers in the network, whereas in broadcasting, we have a broadcast address by which we send packets to all the routers.
In OSPF, "Router ...
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Best path in BGP Routing
Assuming 'Network A' is having 2 ISPs which are directly connected to 'Network B', which path will be used to connect to 'Network B'?
Network A --> IP Transit A / IP Transit B --> Network B
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Network Neutrality, how does it actually work, technically speaking?
In this NPR article there is mentioned 'network neutrality' with very little details on what it actually is or how it actually works. I tried researching it on my own but I get a lot of non-technical ...
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How would a router with /32 WAN subnet mask communicate with the rest of the Internet?
I'm studying networking and one of the most basic things I've been told countless times is that computers can't communicate outside of their own subnet.
On the other hand, by looking at some ADSL ...
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Why use iBGP inside an Autonomous System, if IGP protocols fulfill the need for internal communication
Can anyone explain why we need iBGP for the routes when we have the IGP protocols (OSPF, RIP) for internal communication within the AS?
I have read a lot of articles and books, but I could not find ...
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Difference between access list and prefix list?
Can someone explain with an example whats the difference between an access list and prefix list.
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CEF operations on L3 switch vs router
I understand that L3 switches use CEF for faster packet forwarding. However, CEF will not work for packets that need to undergo NAT. Does this mean CEF isn't used by edge routers and edge L3 switches? ...
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Why are IP addresses given to each interface and not device? What would the implications of that be?
Why do we need to give IP addresses to each interface? Wouldn't giving one to each device be enough?
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What are the differences between VRRP and HSRP?
Are there any significant differences between VRRP and HSRP?
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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 ...
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Why does OSPF need Type2 LSAs?
Learning more about OSPF for CCNP studies. I'm looking at how OSPF builds its links, and have just covered Type1 LSAs. Looking at Type1 LSAs, I'm wondering why these are even necessary?
The book ...
- 3,300
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RIB vs FIB differences?
Can someone explain the differences between a RIB and FIB a little further? I didn't see any similar questions on the site so I thought this would be a good addition. The RIB routes and the FIB ...
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OSPF Stuck in Exstart Adjacency State
According to this article two routers will get stuck in the exstart adjacency state when their configured MTU sizes do not match. Does a VLAN tag affect this as well even if the routers involved are ...
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Whats's the function of a loopback interface in routing protocols?
So I've got this task where I have to setup a virtual network with an OSPF routing protocol. I firstly ignored this loopback interface I had to configure on the routers since it didn't do any ...
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OSPF or iBGP for interior routing protocol?
So the plan is, two core routers each with a eBGP session to one of two ISPs with full routes. Both routers publish their full tables to each other so they can control traffic flow more intelligently ...
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How to provide failover for space-diversity T1
I have inherited a small, insular, dedicated network which is essentially trouble-free, so naturally I want to improve it :-) I lowered my network knowledge and savvy to somewhere around a 2 to 3 on ...
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Cisco NAT hairpinning
I have a Cisco router configured NAT (4 static NAT and dynamic NAT). My problem is that I can't access internal servers using public IP addresses from the internal network.
I know what the problem ...
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Something is filling my force10 ARP table
I have 2 force10 s25 switches that are used for a dark fiber link between two school buildings. One of my switches is filling its ARP table to the brim and then failing. This can happen as often as ...
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Why do I get "% Warning: use /31 mask on non point-to-point interface cautiously" when I use a /31 subnet mask?
Why do I get % Warning: use /31 mask on non point-to-point interface cautiously when I use a /31 subnet mask over Ethernet, and why am I not able to ping from R1 to R2 when both the interfaces have ...
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Configuring a Cisco ASA 5505 for routing
I'll start by pointig out that networking issues have always left me scratching my head. There is something about routing especially that I just haven't had that "Oh I get it" moment yet, so it's ...
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Problem with VPN tunel from remote location through ISP (PPTP)
I have network situation like this:
ISP Router (modem) - device given to us by our ISP - modem & router in one but it is set into transparent mode - ISP say so ;D we have to find it that it is ...
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OSPF and its use of Multicast
When it comes to OSPF and its use of multicast, am I correct in believing that IGMP forwarding and an IGMP querier is still required within the local segment?
My understanding would be without this, ...
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