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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9
votes
2answers
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. ...
2
votes
2answers
3k views

SonicWALL NSA 220 degraded egress performance

We have a SonicWALL NSA 220 running SonicOS Enhanced 5.8.1.2-20o. Our ISP provides a symmetrical 100/100 ethernet handoff. Performance on the ingress achieves the full 100Mbps while egress only ...
13
votes
5answers
14k views

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 ...
15
votes
3answers
20k views

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 ...
2
votes
0answers
557 views

How to force route for MIP in screenos, multiple ISP untrust

Scenairo: SSG140 in HA configuration. Four interfaces: LAN (trust) eth0/0 172.20.0.0./24 ISP1 (untrust) eth0/1 1.1.1.130/28 ISP2 (untrust) eth0/2 2.2.2.194/28 ISP3 (untrust) eth0/3 3.3.3.130/28 ...
3
votes
1answer
4k views

OSPF between ASA and IOS: Subnet and area design

Network: 100.10.0.0/21 R1, 100.10.0.9/29 (loopback 100.10.0.1/32) R2, 100.10.0.10/29 (loopback 100.10.0.2/32) ASA (active), 100.10.0.11/29 ASA (passive), 100.10.0.12/29 R1 has two bgp transit ...
1
vote
1answer
523 views

ECMP between next-hops with different route prefix length

I have a basic question about ECMP, say I have a /20 route and also a /16 route to a host, and both are reachable, can ECMP load-balance between different prefix length or is it like, hardware first ...
1
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3answers
168 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 ...
5
votes
2answers
480 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 ...
7
votes
1answer
10k views

Cisco PBR verify-availability with interface instead of next-hop

We have a number of Cisco 891 routers configured with dual WAN links. All of these routers are running Cisco IOS 15.x In some cases, we use policy based routing to force particular traffic down one ...
3
votes
1answer
945 views

Difference between RREQ ID and DestSeqNum in RREQ packet of AODV protocol?

What is the difference between RREQ ID and Destination Sequence number (DestSeqNum) in RREQ packet of AODV protocol? DestSeqNum in RREQ packet is used for a reverse route maintaining and should be ...
1
vote
2answers
1k views

ASA 5510 + 3550

I'm looking to host a few workloads for friends. I have an ASA5510 and a 3500 switch. We plan to have a few VLANs behind the switch, all sharing the single internet connection. I was thinking of ...
5
votes
4answers
403 views

BGP for Internet connection

Currently i'm CCNA and going for CCNP. I have a qustion about BGP. Why would companies use BGP for Internet connection? Thank you in advance.
6
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3answers
11k views

OSPF and routing table

I have several questions on OSPF. 1 OSPF is a link-state prototol, so routers inside an AS only broadcast their link states to all the other routers. I'm wondering if a router doesn't tell other ...
10
votes
1answer
2k views

QoS between two VLANs with Cisco 881 Router (IOS)

I'm hoping to get some advice regarding the best practice to delegate a limited Internet connection between two VLANs. In my case, one VLAN is for an office network, and the other is for guests. What ...
2
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5answers
298 views

Need Clarification Regarding VPN and Routing

I have my topology as follows ... ---------------------- | | | LAN-1 | | (192.168.2.0/24) | | | | | | | -----...
20
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4answers
21k 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 ...
6
votes
1answer
8k views

Cisco ASA cannot get “inside” vlan to internet through “outside” vlan

I just got my outside vlan configured up-and-running See Post Here. I was able to get vlan 2 pinging to the internet 8.8.8.8 specifically. However, now I honestly think I am misunderstanding what ...
6
votes
1answer
319 views

Do we have an SNMP MIB for URIB

As we know that URIB (Unicast RIB) holds various route entries that have been added by routing protocols running on the box (like BGP, EIGRP, etc). Typically, "show ip route" woudl display all entries ...
8
votes
1answer
2k views

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 ...
14
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2answers
1k views

BGP regular expression .+_.+_.+_.+_.+_.+_.+_.+_.+_.+_.+_.+

could anyone tell me what ip as-path access-list 100 deny .+_.+_.+_.+_.+_.+_.+_.+_.+_.+_.+_.+ stands for?! I searched over the internet for the meaning of this regular expression, but I was unable to ...
3
votes
1answer
807 views

Destination node sequence number increment policy

I read the following from RFC 3561 - AODV, page 11: A destination node increments its own sequence number in two circumstances: - Immediately before a node originates a route discovery, it MUST ...
4
votes
2answers
4k views

AODV sequence numbers and loop prevention

I am learning about the AODV (ad-hoc on-demand distance vector) protocol. I saw a "sequence number" with a value like "A 46"; however, I don't understand why incrementing this sequence number can ...
10
votes
1answer
4k views

How would one route an IP network through different ISPs?

So, if I have a site that has 2 (or more) internet connections, with a routable IP subnet that I own, and one ISP goes down, how do I tell the rest of the world to send traffic addressed to my network ...
4
votes
3answers
271 views

Router neighbour config discovery

I am new to the whole networking world and I apologize if this is a re-post of a question. What I want to know is that is there a mechanism for routers to discover its environment. NOT what a ...
6
votes
1answer
191 views

Originate Customer AS

We have a customer who we are advertising full routes to, and he is sending prefixes to us. However, the customer wants his ASN to show in the as path for his /24. Right now his /24 is terminating ...
1
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3answers
2k views

IPv4 & IPv6 IPSec differences

I am an undergraduate student where I decided to develop a firmware that would eliminate the security vulnerabilities that exist within the current technologies used. such as tunneling, translation ...
12
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2answers
10k views

Error: `EIGRP is restricted to stub configurations only on this platform`

We just bought some new Cat4507R+E distribution switches. When we bought the switches, we asked for an Advanced Services K9 image, but our reseller told us they only come with a Universal K9 image. ...
7
votes
3answers
1k views

Alternatives to multiple Service Providers

I have one SP right now that serves 100 Sites and we are currently planning to migrate all the sites to a new SP. However, this will be a phased migration, so we will have some sites in the new SP ...
18
votes
3answers
1k views

How does multihoming work with ipv6?

What are the differences between multihoming in IPv4 versus IPv6? Can an enterprise request a provider-independent IPv6 address space from its RIR/LIR which can be advertised to multiple upstream ...
5
votes
3answers
270 views

Are VPN Routers the same as a Router

I'm currently looking at the Cisco RV042 VPN router, and I am wondering if I will be able to setup individual networks with it. How do I know which routers or firewalls are capable of setting up ...
5
votes
1answer
1k views

Layer 3 network, multiple internet connections

I'm using a Procurve 5406zl (J8697A) layer 3 switch with multiple vlans: VLANs: v10 Main Network 10.1.4.1 v12 Wireless 10.1.8.1 v13 Restricted Wireless 10.0.0.1 v14 Tech 192.168.7.1 v50 Internet 192....
10
votes
3answers
4k views

3 subnets, 2 OSPF areas - Will This Work?

Will any issues occur if I have a topology involving 3 subnets and two OSPF areas where one subnet is in AREA 0 and the other two subnets are both in AREA 1? For example: [area 1, subnet 1]---[ABR #...
6
votes
4answers
21k views

Reconfiguring Layer3 Switch to enable IP routing and become the default gateway

Current configuration with HP Procurve 2848 switch at a colocation facility consists of using the ISP switchport as the default gateway. The current configuration is very basic with only 1 vlan assign ...
5
votes
6answers
608 views

Can the same network IPs be used more than once

Because of how routers separate networks is it possible to say use the network 192.168.1.0/24 several times as long as you have enough networks to separate? Example: 192.168.1.0/24 <--> 172.16.0....
2
votes
1answer
340 views

Static routing in Linux [closed]

I want to know how static routes are evaluated in Linux. Have a few more specific questions. How are metrics used? If the packet is the last hop what do I put in the next hop field of the route? For ...
12
votes
3answers
11k views

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 ...
3
votes
5answers
19k views

Routing Serial cables instead of Ethernet

I am doing some CCNA training videos and using packet tracer and they showed using a serial cable to connect two routers. Why are serial cables used instead of Ethernet cables? Does it depend on the ...
3
votes
3answers
558 views

How do apps know about asymmetric routing?

We made did a campus LAN upgrade recently, during which we migrated from a mixed EIGRP/OSPF IGP to a multi-area OSPF redistributing to/from BGP on our WAN. We have two entry points on different sides ...
2
votes
2answers
2k views

loopback ip issue

So I have a weird issue. If I configure a /30 ip on an ethernet interface, for example 10.10.10.1/30 on Router1 and 10.10.10.2/30 on an ethernet interface on Router2, I can ping each other fine...no ...
3
votes
1answer
1k views

ASA Transparent Mode Route Lookup

In what situations will an ASA perform route lookup? (transparent mode)
1
vote
3answers
790 views

How to keep office LAN private from public WLAN [closed]

I handle the network at a small business; it's not my primary job but one that I am in charge of. My boss owns a house next to the office that he uses as a general meeting area and as a guest house ...
15
votes
2answers
9k views

BGP multipath with different ASNs feasible for production networks?

on Cisco (this command is hidden for some reason) #bgp bestpath as-path multipath-relax The default BGP behavior only installs only routes with exact the same AS_PATH into RIB. With multipath-relax, ...
6
votes
3answers
270 views

/23 PI space - breakup

a client currently has a /23 PI space where the route-object is currently managed by ISP-A we want to split the PI space into two /24's but not certain on how best to go about this. ISP-A will use ...
11
votes
3answers
1k views

Do today's routers prevent fake IP headers?

I know people can modify the IP headers and change source IP address, but it should be simple for network devices to detect those messages. If they don't, why is it so hard? Does it add too much ...
14
votes
6answers
22k views

What happens when the ARP cache overflows?

In at least one implementation there is a hard limit on the capacity of the ARP table. What happens when the ARP cache is full and a packet is offered with a destination (or next-hop) that isn't ...
8
votes
1answer
979 views

traffic engineering - policies for BGP vs static routes

Considering a transition of specific public Internet site via a new location. At the current location, I've got a static route configured in my Cisco router pointed to my internal firewall. The new ...
11
votes
3answers
7k views

interpreting ping results

I'm pinging yahoo.com and am I'm puzzled by the result. C:\Users\jon>ping -t yahoo.com Pinging yahoo.com [98.138.253.109] with 32 bytes of data: Reply from 98.138.253.109: bytes=32 time=195ms TTL=...
7
votes
2answers
785 views

ISIS p2p on Ethernet media

I am looking for technical clarity on why someone should / shouldn’t use ISIS p2p topologies on Ethernet media. Ethernet is a broadcast medium , however if it’s configured as a p2p link with /31’s ...
2
votes
1answer
1k views

Portforwarding by Subdomain [closed]

I want to have multiple servers behind a single firewall and access each with a different subdomain. Currently, I am having to have each server tied to a different port (which my firewall forwards to ...