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Questions tagged [gre]

Generic Routing Encapsulation is a tunnelling protocol, used to carry network layer protocols through encapsulation inside others.

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1answer
26 views

Use cases for GRE over IPSEC

I'm trying to understand use cases for GRE over IPSEC. In the diagram below, each site uses GRE to encapsulate multicasts associated with OSPF. (There is still a requirement to configure SAs between ...
2
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1answer
35 views

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 ...
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1answer
34 views

Encrypt Gre tunnel traffic

I have a gre tunnel between vyatta and juniper srx . I would like to encrypt the gre tunnel traffic if its possible. thanks Pratik
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1answer
28 views

Network Security Tunnel

In the Tunnel Interface, when I edit the tunnel information, it shows: Attributes Values Tunnel Source IF10 Tunnel Destination 1.0.0.1 Tunnel Mode GRE What does IF10 ...
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0answers
68 views

Not able to ping through GRE Tunnel

I'm trying to build a GRE tunnel between two Ubuntu machines. I followed this Documentation to avoid all problems, the 2 concerned interfaces are directly linked and are in the same subnet 10.0.41.0/...
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2answers
391 views

GRE-IPsec Tunnel between Cisco Router and a Linux Router

I am trying to create a GRE/IPsec tunnel between Cisco router and a Linux Router. The tunnel is UP and active, but when I do a "show crypto session" on the Cisco router the Active SA's keep on ...
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2answers
126 views

TTL, GRE tunnel

I need some advise on the TTL. Currently my application vendor sets TTL to be with value 1 and he should increase it. He is thinking about value of 10, but I'm not sure that this is enough: Assuming ...
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1answer
61 views

Is it possible to append custom data to every packet of a request? [closed]

For an end-to-site VPN, i.e. where a device (VPN client) is responsible for encapsulating the GRE packet, is it possible to send some custom data along with the GRE packet beyond just the standard ...
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1answer
108 views

How to use ACL to deny sending packages to the GRE tunnel?

I need to do a small lab. The topology is shown on the image below: What I need to do, is make static routing so all routers can ping each neighbour's physical interface, configure a GRE tunnel ...
2
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1answer
185 views

PPP CHAP Authentication password requirement

What is the requirement for CHAP authentication on a PPP interface? I thought both routers had to have the same password defined, such as below. r1> username r2 password demo r2> username r1 ...
3
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2answers
325 views

OSPF on tunnel interfaces

Can I keep different tunnel interfaces in different OSPF areas. Keep in mind that the physical interface is going to be the same
3
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3answers
195 views

Layer 3 tunnel with Dynamic IP address

I want to ask whether it is possible to configure Layer 3 Tunnel with the two end points/interfaces have dynamic IP address? If the interface IP change, the tunnel will have to be re-negotiated, is ...
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1answer
56 views

Qos implementation

I want to implement Qos on a GRE tunnel and want to give priority to a destination IP 1.1.1.1 of a system from our site using WAN link. I will match the traffic through an ACL in class-map in which ...
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1answer
75 views

Secure communication between multiple sites over Internet

Does anyone know what would be the best practice to securely connect 2 or more branches with HQ over the Internet, and to allow communication between all of them (so anyone can contact anyone) if I ...
2
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1answer
487 views

MPLS over GRE tunnel with Linux iproute2 [closed]

I'm trying to encapsulate IP packets in MPLS, transported over a GRE tunnel between two Linux hosts (a and b). a has 10.199.0.1 on GRE tunnel interface foo4, while b has 10.199.0.2 on GRE tunnel ...
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2answers
3k views

What is the difference between L2TP vs GRE

Can anyone clearly explain that what is the difference between L2TP and GRE tunnel? Is L2TPv3 Any different I am trying to understand where these protocol are used and why we use L2TP instead of ...
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1answer
322 views

GRE over IPSec vs L2TP over IPSEC

Every single VPN provider offers L2TP over IPSec. What is the reason GRE over IPSec is never offered ? Is there any downfall ? It seems to be exactly the same.
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1answer
602 views

Different tunnel modes (protected with ipsec)

I’m doing a connection of 2 sites in ipv6 over an ipv4 network. I thought to do a tunnel between this 2 sites and protect it with IPsec. But I saw there are different types of tunnels (by default GRE):...
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2answers
356 views

Site-to-Site VPN tunnel configuration

I remember in uni that we implemented VPN tunnels always on the border routers and then use GRE tunnels to connect between two remote subnets. I was always told that VPN tunnels need to know the ...
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2answers
83 views

Cisco IPSec questions on loopback0 and phase 2

ip multicast-routing crypto isakmp policy 2 encr 3des hash md5 authentication pre-share crypto isakmp key 123 address 1.7.129.10 ! crypto ipsec transform-set remotevpn esp-3des esp-md5-hmac ! ...
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1answer
464 views

Is a GRE tunnel sensitive to packet loss?

I tested a GRE tunnel on a lousy link, and all traffic seems lagging and slow, but when I switch to a healthy link, everything run smoothly. Is a GRE tunnel, in general, very sensitive to packet loss?...
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1answer
433 views

Regarding front door vrf concept

While reading up on front-door vrf concept here, i am just wondering , what if we made the network statements more precise/specific or used different subnets altogether, we would never have our tunnel ...
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1answer
231 views

Regarding Gre tunnel encapsulation

Please consider the attached image below: A GRE tunnel is set up between R1 and R4. Tunnel source is R1 interface having the IP address 172.16.0.1/16 Tunnel destination is R4 interface having the IP ...
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1answer
692 views

Regarding Multicast over the internet

I was going through the use cases of GRE tunnel and see that it is also used to carry multicast traffic over the internet.I understand that multicast IP belongs to class D address which is a public IP ...
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0answers
2k views

Tunnelling difference over VXLAN vs NVGRE vs GENEVE

Any bullet points that are most imp points when it comes differences between these three tunnellings VXLAN/NVGRE/GENEVE in networks. Found some notes here, anything that you may like to add would be ...
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0answers
203 views

fVRF's and gre keepalives

If you are using front door VRF's (fVRFs) for a static GRE tunnel I can find no way to use keepalives across the tunnel to keep it from always being in an up/up state. I'm assuming this is an issue ...
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1answer
584 views

More Fragment flag and Frag Offset field after GRE fragmentation

If the length of a packet by attaching GRE-IP header results in bigger size than router MTU, what happen on More Fragment Flag and Frag Offset field of that packet?
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3answers
4k views

GRE over IPsec between Juniper SRX100 and Fortigate 100D

I need assistance configuring VPN setup between Fortigate and Juniper devices (GRE over IPSec). I have the topology as follows: What I need to do is create a route-based IPSec tunnel between the ...
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2answers
589 views

Packet flow in GRE Tunnel

In the below image what would be the ip address in the outer ip header when packet goes from R1 to R2. If the ip address in the outer header is 172.16.0.1 , how does it travels the internet as its not ...
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1answer
1k views

Why source and destination addresses should match in GRE tunnel?

In a GRE tunnel, when R1 (public IP 172.16.0.1, tunnel address 10.0.0.1) sends a packet to R3 (public IP 172.16.0.6, tunnel address 10.0.0.2) and R3 receives it, the following happens: A packet is ...
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1answer
76 views

How would “looping” in GRE occur according to RFC 2784

RFC 2784 mentions: Care should be taken when forwarding such a packet, since if the destination address of the payload packet is the encapsulator of the packet (i.e., the other end of the tunnel), ...
2
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1answer
65 views

Why specify the source tunnel address?

http://www.firewall.cx/cisco-technical-knowledgebase/cisco-routers/868-cisco-router-gre-ipsec.html Let me use the same example as in my previous question. R1(config)# interface Tunnel0 R1(config-if)#...
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1answer
2k views

Two GRE tunnels in one subnet

http://www.firewall.cx/cisco-technical-knowledgebase/cisco-routers/868-cisco-router-gre-ipsec.html In the example above, R1: R1(config)# interface Tunnel0 R1(config-if)# ip address 172.16.0.1 255....
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2answers
254 views

Splitting Data and Voice by creating GRE tunnel for Data, using overhead for Voice

A client: 3 sites with L2 links to our Data Centre. I create L3 links by providing IP's both sides. I want to create a GRE tunnel over each link with seperate IPs in order to route Data over these new ...
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2answers
385 views

Support GRE tunneling router or firewall

I am new member of Network Engineering site! These days I am interested in GRE tunneling. I know that GRE is developed by CISCO and many routers produced by CISCO and Juniper support GRE tunneling. ...
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1answer
2k views

What is the difference between ip nhrp nhs and ip nhrp map?

These two commands seems similar when I configure a DMVPN Spoke. What is the difference? interface Tunnel1 ip address 192.168.88.2 255.255.255.248 no ip redirects **ip nhrp map 192.168.88.1 10.0.1....
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0answers
752 views

GRE tunnel(or even any tunnelling technique) between Alcatel 7750 and a Cisco Router

has anyone on here been able to successfully create a GRE tunnel or any kinda of tunnelling mechanism between an Alcatel router and a Cisco router. I've been struggling with this and for a while and ...
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0answers
108 views

Overlay network with GRE without spanning tree

I need to create an overlay network with potential of hundreds of servers (each is an hypervisor and running a open vswitch). I'm going to use ovswitch and connect each server to all other servers ...
3
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1answer
2k views

Transparent proxy (wccp and squid)

I am trying to solve problem about configuration of transparent proxy server. I don't have any configuration on devices, I have not started yet. Because of preparing and studying that topic. I am ...
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3answers
192 views

Can different networks connected by MPLS run the same OSPF area?

I was wondering if two different OSPF areas connected via an MPLS/GRE tunneled link run OSPF across them? May be keeping the interconnecting MPLS/GRE routers in OSPF backbone area 0?
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2answers
729 views

What problem does GRE solve?

As per the RFC, GRE (Generic Routing Encapsulation) specifies a protocol for encapsulation of an arbitrary protocol over another arbitrary network layer protocol. I don't think I understand ...
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1answer
544 views

DSCP trust over IPSec GRE

I have 2 branch offices connecting together via a metro-e and I'm running an ipsec gre tunnel between the 2 sites. routerA=branch1 routerB=branch2 WAN-------routerA----------|metroe|------------...
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0answers
48 views

How is my GRE-Tunneled packet being routed? [duplicate]

I'm trying to figure out exactly what is happening when I create a GRE tunnel. My network looks like this (-> means directly connected): Computer A (eth0: 10.0.1.1) -> (eth0: 10.0.1.2) Router B (...
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3answers
13k views

Stuck at GRE troubleshooting with recursive route

As with my last question, I am learning for my CCNA exam and currently I am bashing my head against the wall, while trying to solve "7.2.2.4 Troubleshooting GRE" I'll explain the topology in a second....
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3answers
1k views

GRE Tunneling on Cisco IOS - Destination Address

What is the reason that you cannot set the tunnel's other side as destination address? Is this because it is virtual only? 192.168.1.0/30 is the subnet I'm using and this is my configuration: ...
3
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2answers
951 views

Alternatives to GRE for multicast over MPLS?

I have an application that requires multicast across our MPLS WAN, and had been using GRE tunnels to facilitate this until recently when I replaced some aging edge routers with HP L3 switches. To my ...
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7answers
9k views

Dynamic Routing Protocol (IGP) over IPSec VPN tunnels to branch offices?

What are the best practices for running an IGP to learn networks at HQ from branch offices when those offices connect via IPSec LAN-to-LAN VPN tunnels over the Internet? The branch offices terminate ...
12
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3answers
3k views

ALU interop GRE tunnel

I've been trying to figure out how to setup a GRE tunnel between an ALU 7750SR and a 3rd party vendor. I think it's balking at the VC-ID in the SDP but i'm hoping someone has experience getting a GRE ...
18
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4answers
1k views

Is GRE necessary for an IP-only tunnel?

I need to build a simple point-to-point tunnel to connect an office through an area of the network we trust but directly don't control. Does the tunnel need to be GRE-encapsulated or can I use direct ...