Managing Route-Map based MPLS VPN

1) How to derive the VPN information of the MPLS VPN configured using route-maps? As I understand, stitching route-maps information to derive VPN is complex as it is difficult to derive & correlate the filters tied to each of the route-maps that are tied to a VRF :(
2) Is there any MIB to get from the MIB
a) Route-maps tied to each VRF
b) What is the filter associated with each route-map?
c) Definition of each of the above filter
It would have been nice if the route-maps' name had global-significance within AS, so that we could have treated route-maps, pretty much like the route-tragets. Alas, I doubt it is :(
It should be noted here that if the MPLS VPN is configured using route targets, the VPN information derivation is fairly straight forward throught MplsVpn MIB.
So, the question is what is the simplest way to derive the MPLS VPN info given that they are configured using route-maps in BGP for labelled-route-distribution & for the pkt association with the VRFs.
Thanks,
Suresh R

Each CE in a customer VPN is also added to the management VPN by selecting the Join the management VPN option in the service request user interface.
The function of the management route map is to allow only the routes to the specific CE into the management VPN. The Cisco IOS supports only one export route map and one import route map per VRF.
http://www.cisco.com/en/US/products/sw/netmgtsw/ps4748/products_user_guide_chapter09186a0080353ac3.html

Similar Messages

Injecting Global default Routes into a MPLS VPN

Hi,
I have a PE router running MPBGP which receives two default routes to the internet through an IPV4 BGP session. I need to import these routes in to a VRF and export them to different customer VRFs so that these VRFs are able to access Internet.
I have used the feature called "BGP Support for IP Prefix Import from Global Table into a VRF Table" (URL:http://www.cisco.com/en/US/products/sw/iosswrel/ps5207/products_feature_guide09186a00803b8db9.html#wp1063870)
and imported these routes into a VRF.
The issue is these routes are not propagated to any of the other PE routers which has customer VRFs configured.
Has anybody tried this or a similar method to inject a dynamic default route into a MPLS VPN.
Any suggestions would be highly appreciated.
Thanks
Subhash

Hi Subhash,
is there anything preventing you from terminating your internet BGP sessions in a VRF? Then everything should go smoothly, i.e. standard VRF import/export.
So possibility A) create a VRF Internet, move bgp neighbor commands there and use filters preventing anything but the default route, then use route targets to distribute the default route into other VRFs.
Possibility B) use static routing with packet leaking. Could look like this:
ip route vrf Internet 0.0.0.0 0.0.0.0 global
ip route vrf Internet 0.0.0.0 0.0.0.0 global 250
ip route Serial0/0 !assuming this is where the customer router connects.
Note: the BGP peer IP does not have to be directly connected! There has to be a LDP label for it though. so include your BGP peers network into your IGP and the backup will work, when you loose the link to the peer.
Hope this helps! Please rate all posts.
Regards, Martin

Route Leaking in MPLS/VPN Networks (IOX support)

Hi all,
I would like to if IOX of CRS-1 can support route leaking between VRF<>Global routing table?
hhttp://www.cisco.com/en/US/tech/tk436/tk832/technologies_configuration_example09186a0080231a3e.shtmlttp://www.cisco.com/en/US/tech/tk436/tk832/technologies_configuration_example09186a0080231a3e.shtml
Regards

Hi,
You can use the vrf keyword after the prefix you want to join and before specifying the NH. It will tell the router in which VRF the lookup should be done:
http://www.cisco.com/en/US/docs/routers/crs/software/crs_r4.0/routing/command/reference/rr40crs1book_chapter9.html#wp172562637
The vrf name "default" is reserved to reference the GRT.
HTH
Laurent.

L3-MPLS VPN Convergence

Perhaps someone on this group can identify the missing timers/processing-delays in end-to-end client route convergence
Scenarios:
a) BGP New route Advertised by Cleint(CPE1)
b) BGP Route withdrawn by Client(CPE1)
PE-to-RR i-M-BGP (Logical)
========= ----RR------ ======
" | | "
CPE1---->PE1------->P1-------->P2---->PE2----->CPE2
| |
--------->P3-------->P4-------
Routing:
- eBGP btw CPE and PE (any routing prot within Cust site),
- OSPF, LDP in Core,
Timers/Steps I'm aware of:
- Advertisement of routes from CE to PE and placement into VRF
- Propagation of routes across the MPLS VPN backbone
- Import process of these routes into relevant VRFs
- Advertisement of VRF routes to attached VPN sites
- BGP advertisement-interval: Default = 5 seconds for iBGP, 30 for eBGP
- BGP Import Process: Default = 15 seconds
- BGP Scanner Process Default = 60 seconds
Would appreciate if you someone can identify any missing process-delay, timers? specially w.r.t RR.
Thanks
SH

Check the LDP/TDP timers in the core. Remember if a link fails in the core, reroute occurs, LDP/TDP binding needs to be renewed. tags are binded on those routes being in the routing table (IGP). So, there is a delay possible from a core prespective:
mpls ldp holdtime
mpls ldp discovery hello [holdtime | interval]
In case you are using TE check these:
mpls traffic-eng topology holddown
mpls traffic-eng signalling forwarding sync
mpls traffic-eng fast-reroute timers promotion
I believe the latter one onyl applies to SDH. In which you use segment loss feature.
Regards,
Frank

Viewing MPLS/VPN packet

Hi there,
I would like to know, is there any features on cisco router to view mpls/vpn packet swapping here and there at P,PE or CE routers especially in service provider networks just like "sh ip cache flow" ?
thanks in advance.
maher

MPLS-aware NetFlow should provide you with this functionality. For more information, please refer to the following link:
http://www.cisco.com/en/US/partner/products/sw/iosswrel/ps1829/products_feature_guide09186a008012dc80.html
Hope this helps,

Selective Route Import/Export in MPLS VPN

Champs
I have multiple brach locations and 3 DC locations.DC locations host my internal applications , DC's also have central Internet breakout for the region. My requirement is to have full mesh MPLS-VPN but at same time brach location Internet access should be from nearest IDC in the region if nearest IDC is not availalbe it should go to second nearest DC for internet.I have decided which are primary and seconday DC for Internet breakout. How can this be achieved in MPLS-VPN scenario.Logically i feel , i have to announce specific LAN subnet and default route(with different BGP attribute like AS Path) from all 3 DCs. Spokes in the specific region should be able to import default route from primary DC and secondary DCs only using some route filter?
Regards
V

Hello Aaron,
the route example works for all routers except the one, where the VRF vpn2 is configured. What you can do for management purposes is either to connect through a neighbor router using packet leaking or configure another Loopback into VRF vpn2.
The last option (and my recommendation) is to establish another separate IP connection from your NMS to the MPLS core. Once VRFs are failing (for whatever reason, f.e. erroneously deleted) you might just not get connectivity to your backbone anymore to repair what went wrong.
So I would create an "interconnection router" with an interface in the VRF vpn2 and one interface in global IP routing table. This way you will still be able to access PEs, even if VRFs or MBGP is gone.
Hope this helps! Please rate all posts.
Regards, Martin

Mapping Model in MPLS VPNs

Hi:
Based on paper titled "L3 MPLS VPN Enterprise Consumer Guide" page 52, figure 44. (http://www.cisco.com/en/US/partner/netsol/ns465/networking_solutions_white_papers_list.html).
1) The figure discards the "streaming video" and "bulk data" traffics within the mapping process. Why? What happens with these traffics? Both traffics are discarded or simply they need to be mapped to "Best Effort"? Please explain.
2)In the same figure, "Interactive Video" is mapped to "Realtime" SP class with "Voice" traffic. Is this "Interactive Video" traffic always no TCP-based? If the opposite is true, why is it mixing TCP & UDP over the same "Realtime" class?

Hi,
That articles mentions that these protocols tend to use transport-layer protocols such as UDP and RTSP. That is true but there are a lot of different streaming protocols around and some of them do use TCP. In fact, even RTSP supports the use of TCP. And you can also stream via HTTP (Windows Media supports this, for example).
So you see, there can be a mix of TCP and UDP traffic here.
The other, more critical, reason for not mixing interactive-traffic with streaming (one-way) traffic is the drastically different jitter/latency requirements for the two. Streaming traffic will easily sustain latency in the order of seconds and jitter is not even a problem. Whereas interactive traffic will not. That is why you should not mix the two.
Hope that helps - pls rate the post if it does.
Paresh

Configuring MPLS VPN using static routing

Hi,
I am managed to set up a BGP/MPLS VPN in a laboratory using CS3620 routers running IOS 12.2(3) with ISIS. I am thinking of using static routes among the PE and P routers instead of a IGP. Does anyone know if Cisco routers supports static configuration of LSP? I have tried but could not get it work.

You can very well run MPLS with static routing in the core, as in Cisco we have to meet 2 criterias to have a MPLS forwarding Table.
1) Creating the LIB
This thing lies in having LDP neighborship netween two peers and you have Label bindings.
This is irrespective of what is the best next hop to reach the advertising peers LDP_ID.
2) Creating the LFIB
Now after considering all the Label bindings, the LDP_ID which can be reached out an interface
as a next hop, those Label bindings get installed in the LFIB.
So considering the above two points, we have to be careful in static routes
only for interfaces like Ethernet (Multiaccess Segments).
As in CEF when you give a static route pointing to an Ethernet Interface, CEF creates a
GLean Adjacency (Meaning there could be multiple hosts as the next hop on this segement, and it will glean for the right next-hop)
Now you may observe that when you give a static route only pointing to an Ethernet interface,
you LDP adjacency may come up and you may exchange the bindings with each other. But the Label Forarding Table is not created. This is bcos of this being a Multiaccess interface. And you have
Glean For it. If its a Normal WAN interface like Serial or POS, then there is no problem of
GLean and you would have a Valid Cached Adjacency.
So to avoid probelems with Ethernet interfaces you can simply specify the next-hop-ip address.
For Eg: ip route 10.10.31.250 255.255.255.255 10.10.31.226 (Without the Interface)
ip route 10.10.31.250 255.255.255.255 fa0/0 10.10.31.226 (Or with the Interface)
Only Difference in both is in the first one it has to do a recursive lookup for the outgoing interface. Otherwise both work well. And you can have static routes in your network
running MPLS.
And doing this CEF would would work as it should and you would have a Valid Cached Adjacency.
So this is applicable for Cisco devices which use CEF, including 6500 with SUP720.
HTH-Cheers,
Swaroop

MPLS route map

Is it possible to configure PBR using route maps on the MPLS. We need to do add a different internet route based on extended access-list which will be different from the default route in the MPLS

Hi!
I am not sure about other devices but atleast on 6500/7600, PBR for mpls traffic is not supported in hardware. All the packets will be processed by the CPU and will spike the CPU utilization. So it is not recommended to use PBR for the ip-to-tag path.
Regards,
Niranjan.
(please rate helpful posts)

Redundant access from MPLS VPN to global routing table

Several our customers have MPLS VPNs deployed over our infrastructure. Part of them requires access to Internet (global routing table in our case).
As I'm not aware of any methods how to dynamicaly import/export routes between VRF/Global routing tables, at the moment there are static routes configured - one inside VRF pointing to global next hop, another one in global routing table, pointing to interface inside VRF.
Task is to configure redundant access to Internet. By redundancy I mean using several exit points (primary and backup), what physically represents separate boxes.
Here comes tricky part - both global static routes (on both boxes, meaning) are valid and reachable in all cases - no matter if specific prefix is reachable in VRF or not. What I'd like to achieve is that specific static route becomes valid only if specific prefix is reachable inside VRF. Yea, sounds like dynamic routing :), I know
OK, hope U got the idea. Any solutions/recommendations ? Running all Internet routing inside VRF isn't an option, at least for now :(

Hi Andris,
I did not mean to have a VRF on the CE. The CE would have both PVCs in the global routing table - his ONLY routing table in fact. One PVC would be used to announce routes into the customer specific VPN (VRF configured on the PE). The other PVC would allow for internet access through the PE (global IP routing table on the PE).
dot1q will be ok as well.
This way the CE can be a normal BGP peer to the PE, i.e. there is no MPLS VPN involved here. This allows all options of customer-ISP connectivity.
Example:
PE config:
interface Serial0/0
encapsulation frame-relay
interface Serial0/0.1 point-to-point
description customer VPN access
ip vrf customer
ip address 10.1.1.1 255.255.255.252
interface Serial0/0.2 point-to-point
description customer Internet access
ip address 192.168.1.1 255.255.255.252
router rip
address-family ipv4 vrf customer
version 2
network 10.0.0.0
no auto-summary
redistribute bgp 65000 metric 5
router bgp 65000
neighbor 192.168.1.2 remote-as 65001
address-family ipv4 vrf customer
redistribute rip
CE config:
interface Serial0/0
encapsulation frame-relay
interface Serial0.1 point-to-point
description VPN access
ip address 10.1.1.2 255.255.255.252
interface Serial0.2 point-to-point
description Internet access
ip address 192.168.1.2 255.255.255.252
router bgp 65001
neighbor 192.168.1.1 remote-as 65000
router rip
version 2
network 10.0.0.0
no auto-summary
Of course you can replace RIP with whatever is suitable for you. And don´t sue me when you do not apply required BGP filters for internet access... ;-)
The other option ("mini internet") would be feasible as well. Just make sure your BGP filters are NEVER messed up and additionally apply a limit on the numbers of prefixes in your VRF mini-internet.
Regards
Martin

MPLS VPN routes with core IGP costs

Hi,
Is there any way to use the IGP cost between PEs, and pass that into the VRF prefixes?
For example:
A branch site has 2x CEs (CE-A & CE-B), each with a link to a different PE (PE-A & PE-B). EBGP is used between CE-PE. IBGP Between CE-A & CE-B. CE-C is also connected to PE-B with EBGP.
Without any manual intervention, the link from CE-A to PE-A and the link from CE-B to PE-B would be equal cost away. In reality it would be preferable (in our case at least) for traffic destined to CE-C to use the CE-B to PE-B link, because it would result in a shorter path in the core.
I have been looking for a way to use the IGP metric associated with the VRF route next hop. Ideally, I would like to have the option to copy the IGP cost to next hope into the VRF prefix's MED field... or if you're already using MED as a metric then perhaps the option to ADD the IGP cost to next hope to the existing MED value. I was hoping you would be able to do this with an Import Map on the VRF but I can't see a way of acheiving this.
Is there another way to get this result?
Thanks,
Peter

Hi Giuseppe
Thanks very much for your response but I think perhaps I did not explain my question correctly...
What I was trying to acheive was to influence the rouitng at the branch (CE level with the use of MED), rather than at the PE VRF as you have described with Local Preference.
I would like the branch AS (consisting of CE-A & CE-B) to choose the link between CE-B - PE-B to get to CE-C's networks, because it is directly connected or has an IGP cost of 0.
I'm aware I can do this on CE-B by identifying the prefixes from that AS and applying a route-map on CE-B, but I was hoping there was a solution that would be more automatic and less admin overhead by being able to copy the IGP cost into the BGP MED field, as this would then be sent to the CE-B. The prefix sent from PE-A to CE-A would have a higher IGP cost and so would send a higher MED. I hope what I'm trying to explain makes sense.
If this is not possible (I can't find any reference to such a feature...) then are you aware of any other feature that would result in similar behaviour withou having to manually identify prefixes with route maps? The best I can come up with so far is to tag routes into each PE with a community and use a route-map outbound on PE to CE to add a higher MED value to prefixes that do not contain this same community... Or perhaps this can be done with the SOO attribute. The trouble with this method is it only works for PEs with directly connected CEs. It would be nice to leverage the information in the IGP routing table...
Thanks,
Peter

Ask the Expert:Concepts, Configuration and Troubleshooting Layer 2 MPLS VPN – Any Transport over MPLS (AToM)

With Vignesh R. P.
Welcome to the Cisco Support Community Ask the Expert conversation.This is an opportunity to learn and ask questions about concept, configuration and troubleshooting Layer 2 MPLS VPN - Any Transport over MPLS (AToM) with Vignesh R. P.
Cisco Any Transport over MPLS (AToM) is a solution for transporting Layer 2 packets over an MPLS backbone. It enables Service Providers to supply connectivity between customer sites with existing data link layer (Layer 2) networks via a single, integrated, packet-based network infrastructure: a Cisco MPLS network. Instead of using separate networks with network management environments, service providers can deliver Layer 2 connections over an MPLS backbone. AToM provides a common framework to encapsulate and transport supported Layer 2 traffic types over an MPLS network core.
Vignesh R. P. is a customer support engineer in the Cisco High Touch Technical Support center in Bangalore, India, supporting Cisco's major service provider customers in routing and MPLS technologies. His areas of expertise include routing, switching, and MPLS. Previously at Cisco he worked as a network consulting engineer for enterprise customers. He has been in the networking industry for 8 years and holds CCIE certification in the Routing & Switching and Service Provider tracks.
Remember to use the rating system to let Vignesh know if you have received an adequate response.
Vignesh might not be able to answer each question due to the volume expected during this event. Remember that you can continue the conversation on the Service Provider sub-community discussion forum shortly after the event. This event lasts through through September 21, 2012. Visit this forum often to view responses to your questions and the questions of other community members.

Hi Tenaro,
AToM stands for Any Transport over MPLS and it is Cisco's terminology used for Layer 2 MPLS VPN or Virtual Private Wire Service. It is basically a Layer 2 Point-to-Point Service. AToM basically supports various Layer 2 protocols like Ethernet, HDLC, PPP, ATM and Frame Relay.
The customer routers interconnect with the service provider routers at Layer 2. AToM eliminates the need for the legacy network from the service provider carrying these kinds of traffic and integrates this service into the MPLS network that already transports the MPLS VPN traffic.
AToM is an open standards-based architecture that uses the label switching architecture of MPLS and can be integrated into any network that is running MPLS. The advantage to the customer is that they do not need to change anything. Their routers that are connecting to the service provider routers can still use the same Layer 2 encapsulation type as before and do not need to run an IP routing protocol to the provider edge routers as in the MPLS VPN solution.
The service provider does not need to change anything on the provider (P) routers in the core of the MPLS network. The intelligence to support AToM sits entirely on the PE routers. The core label switching routers (LSRs) only switch labeled packets, whereas the edge LSRs impose and dispose of labels on the Layer 2 frames.
Whereas pseudowire is a connection between the PE routers and emulates a wire that is carrying Layer 2 frames. Pseudowires use tunneling. The Layer 2 frames are encapsulated into a labeled (MPLS) packet. The result is that the specific Layer 2 service—its operation and characteristics—is emulated across a Packet Switched Network.
Another technology that more or less achieves the result of AToM is L2TPV3. In the case of L2TPV3 Layer 2 frames are encapsulated into an IP packet instead of a labelled MPLS packet.
Hope the above explanation helps you. Kindly revert incase of further clarification required.
Thanks & Regards,
Vignesh R P

Dynamic Routing for Failover L2L VPN

Hi,
Can someone offer me some guidance with this issue please?
I've attached a simple diagram of our WAN for reference.
Overview
Firewall is ASA 5510 running 8.4(9)
Core network at Head Office uses OSPF
Static routes on ASA are redistributed into OSPF
Static routes on ASA for VPN are redistributed into OSPF with Metric of 130 so redistributed BGP routes are preferred
Core network has a static route of 10.0.0.0/8 to Corporate WAN, which is redistributed into OSPF
Branch Office WAN uses BGP - Routes are redistributed into OSPF
The routers at the Branch Office use VRRP for IP redundancy for the local clients default gateway.
Primary Branch Office router will pass off VRRP IP to backup router when the WAN interface is down
Backup BO router (.253) only contains a default route to internet
Under normal operation, traffic to/from BO uses Local Branch Office WAN
If local BO WAN link fails, traffic to/from BO uses IPSec VPN across public internet
I'm trying to configure dynamic routing on our network for when a branch office fails over to the IPsec VPN. What I would like to happen (not sure if it's possible) is for the ASA to advertise the subnet at the remote end of the VPN back into OSPF at the Head Office.
I've managed to get this to work using RRI, but for some reason the VPN stays up all the time when we're not in a failover scenario. This causes the ASA to add the remote subnet into it's routing table as a Static route, and not use the route advertised from OSPF from the core network. This prevents clients at the BO from accessing the Internet. If I remove the RRI setting on the VPN, the ASA learns the route to the subnet via the BO WAN - normal operation is resumed.
I have configured the metric of the static routes that get redistributed into OSPF by the ASA to be higher than 110. This is so that the routes redistributed by BGP from the BO WAN into OSPF, are preferred. The idea being, that when the WAN link is available again, the routing changes automatically and the site fails back to the BO WAN.
I suppose what I need to know is; Is this design feasible, and if so where am I going wrong?
Thanks,
Paul

Hi Paul,
your ASA keeps the tunnel alive only because that route exists on ASA. Therefore you have to use IP-SLA on ASA to push network taffic "10.10.10.0/24" based on the echo-reply, by using IP-SLA
Please look at example below, in the example below shows the traffic will flow via the tunnel, only in the event the ASA cannot reach network 10.10.10.0/24 via HQ internal network.
This config will go on ASA,
route inside 10.10.10.0 255.255.2550 10.0.0.2 track 10
(assuming 10.0.0.2 the peering ip of inside ip address of router at HO)
route outside 10.10.10.0 255.255.255.0 254 xxx.xxx.xxx.xxx
(value 254 is higher cost of the route to go via IPSec tunnel and x = to default-gateway of ISP)
sla monitor 99
type echo protocol ipIcmpEcho 10.10.10.254 interface inside
num-packets 3
frequency 10
sla monitor schedule 99 life forever start-time now
track 10 rtr 99 reachability
Let me know, if this helps.
thanks
Rizwan Rafeek

How can I find the all path available for a MPLS VPN in SP network

How can I find the all path available for a MPLS VPN in SP network between PE to PE and CE to CE?

Hi There
If we need to find all the available paths for a remote CE from a local PE it will depend upon whether its a RR or non-RR design. If the MP-iBGP deisgn is non-RR the below vrf specific command
sh ip bgp vpnv4 vrf "vrf_name" will show us the MP-iBGP RT for that particular VPN. It will show us the next hop. Checking the route for same in the Global RT will show us the path(s) available for same ( load-balancing considered) .Then we can do a trace using the Local PE MP-iBGP loopback as source to remote PE's MP-iBGP loopback to get the physical Hops involved.
However if the design is RR-based there might be complications involved when the RR is in the forwarding path ie we have NHS being set to RR-MP-iBGP loopback and the trace using the Local PE MP-iBGP loopback as source to remote PE's MP-iBGP loopback will get us the physical Hops involved.
If we have redundant RRs being used with NHS being set then the output of sh ip bgp vpnv4 vrf "vrf_name" will show us two different available paths for the remote CE destination but just one being used.
RR-based design with no NHS being used will always to cater to single path for the remote CE detsination.
So in any case the actual path used for the remote CE connectivity would be a single unless we are using load-balancing.
Hope this helps you a bit on your requirement
Thanks & Regards
Vaibhava Varma

MPLS/VPN network load balancing in the core

Hi,
I've an issue about cef based load-balancing in the MPLS core in MPLS/VPN environment. If you consider flow-based load balancing, the path (out interface) will be chosen based on source-destination IP address. What about in MPLS/VPN environment? The hash will be based on PE router src-dst loopback addresses, or vrf packet src-dst in P and PE router? The topology would be:
CE---PE===P===PE---CE
I'm interested in load balancing efficiency if I duplicate the link between P and PE routers.
Thank you for your help!
Gabor

Hi,
On the PE router you could set different types and 2 levels of load-balancing.
For instance, in case of a DUAL-homed site, subnet A prefix for VPN A could be advertised in the VPN by PE1 or PE2.
PE1 receives this prefix via eBGP session from CE1 and keep this route as best due to external state.
PE2 receives this prefix via eBGP session from CE2 and keep this route as best due to external state.
                             eBGP
                     PE1 ---------CE1
PE3----------P1                          Subnet A
                     PE2----------CE2 /
                            eBGP
Therefore from PE3 point of view, 2 routes are available assuming that IGP metric for PE3/PE1 is equal to PE3/PE2.
The a 1rst level of load-sharing can be achieve thanks to the maximum-paths ibgp number command.
2 MP-BGP routes are received on PE3:
PE3->PE1->CE1->subnet A
PE3->PE2->CE2->subnet A
To use both routes you must set the number at 2 at least : maximum-paths ibgp 2
But gess what, in the real world an MPLS backbone hardly garantee an equal IGP cost between 2 Egress PE for a given prefix.
So it is often necessary to ignore the IGP metric by adding the "unequal-cost" keyword: maximum-paths unequal-cost ibgp 2
By default the load-balancing is called "per-session": source and destination addresses are considered to choose the path and the outgoing interface avoiding reordering the packets on the target site. Overwise it is possible to use "per-packet" load-balancing.
Then a 2nd load-sharing level can occur.
For instance:
         __P1__PE1__CE1
PE3           \/                   Subnet A
        \ __P2__PE2__CE2
There is still 2 MP-BGP paths :
PE3->P1->PE1->CE1->subnet A
PE3->P1->PE2->CE2->subnet A
But this time for 2 MP-BGP paths 4 IGP path are available:
PE3->P1->PE1->CE1->subnet A
PE3->P1->PE2->CE2->subnet A
PE3->P2->PE1->CE1->subnet A
PE3->P2->PE2->CE2->subnet A
For a load-balancing to be active between those 4 paths, they must exist in the routing table thanks to the "maximum-path 4 "command in the IGP (ex OSPF) process.
Therefore if those 4 paths are equal-cost IGP paths then a 2nd level load-balancing is achieved. the default behabior is the same source destination mechanism to selected the "per-session" path as mentionned before.
On an LSP each LSR could use this feature.
BR

Managing Route-Map based MPLS VPN

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