diff --git a/config/config.yaml b/config/config.yaml
index 6d53288..7c00601 100644
--- a/config/config.yaml
+++ b/config/config.yaml
@@ -22,9 +22,11 @@ uplink:
 downlink:
   - control-uri: "http://[fd00:0:0:0:2:8000:0:4]:8080"
     enabled: true
+    srgw_gtp4: "10.3.0.1"
     segments-list:
       - "fc00:1:1::/48"
   - control-uri: "http://[fd00:0:0:0:2:8000:0:5]:8080"
     enabled: true
+    srgw_gtp4: "10.3.0.1"
     segments-list:
       - "fc00:1:1::/48"
diff --git a/go.mod b/go.mod
index 0724c38..97fc746 100644
--- a/go.mod
+++ b/go.mod
@@ -7,7 +7,7 @@ require (
 	github.com/gin-gonic/gin v1.10.0
 	github.com/gofrs/uuid v4.4.0+incompatible
 	github.com/nextmn/go-pfcp-networking v0.0.42
-	github.com/nextmn/json-api v0.0.16
+	github.com/nextmn/json-api v0.0.17-0.20250117120523-f0c7cb4f9792
 	github.com/nextmn/logrus-formatter v0.0.1
 	github.com/nextmn/rfc9433 v0.0.2
 	github.com/sirupsen/logrus v1.9.3
diff --git a/go.sum b/go.sum
index 7fa3ce3..bef2ea7 100644
--- a/go.sum
+++ b/go.sum
@@ -53,6 +53,10 @@ github.com/nextmn/go-pfcp-networking v0.0.42 h1:kYcGyIUMe/RVt3DpvDOKJt4+UbScIewD
 github.com/nextmn/go-pfcp-networking v0.0.42/go.mod h1:KYoKLiltDmHL2YMU5mz2k/E1xMoz4TpmzTz6Nr5u5gA=
 github.com/nextmn/json-api v0.0.16 h1:RU5eTVvnwrYK0Zmh/EhdO7Q3A+hUWjavg9ytJknaYTU=
 github.com/nextmn/json-api v0.0.16/go.mod h1:CQXeNPj9MDGsEExtnqJFIGjLgZAKsmOoO2fy+mep7Ak=
+github.com/nextmn/json-api v0.0.17-0.20250117102021-8f2d7604eabc h1:WZg8N41u0VIeII/AS5U7aVjPCuGP+c3PdAd782xGxtI=
+github.com/nextmn/json-api v0.0.17-0.20250117102021-8f2d7604eabc/go.mod h1:CQXeNPj9MDGsEExtnqJFIGjLgZAKsmOoO2fy+mep7Ak=
+github.com/nextmn/json-api v0.0.17-0.20250117120523-f0c7cb4f9792 h1:eeigbuE6dbRFWl76iOvP+FgvLtkfgL7d0dRnGDgCJ5w=
+github.com/nextmn/json-api v0.0.17-0.20250117120523-f0c7cb4f9792/go.mod h1:CQXeNPj9MDGsEExtnqJFIGjLgZAKsmOoO2fy+mep7Ak=
 github.com/nextmn/logrus-formatter v0.0.1 h1:Bsf78jjiEESc+rV8xE6IyKj4frDPGMwXFNrLQzm6A1E=
 github.com/nextmn/logrus-formatter v0.0.1/go.mod h1:vdSZ+sIcSna8vjbXkSFxsnsKHqRwaUEed4JCPcXoGyM=
 github.com/nextmn/rfc9433 v0.0.2 h1:6FjMY+Qy8MNXQ0PPxezUsyXDxJiCbTp5j3OcXQgIQh8=
diff --git a/internal/app/rules-pusher.go b/internal/app/rules-pusher.go
index 683cf4a..abdd9b0 100644
--- a/internal/app/rules-pusher.go
+++ b/internal/app/rules-pusher.go
@@ -130,7 +130,7 @@ func (pusher *RulesPusher) pushRTRRule(ctx context.Context, ue_ip string) error
 		return nil // already pushed, nothing to do
 	}
 	infos.Pushed = true
-	service_ip := "10.4.0.1"
+	service_ip := "10.4.0.1" // FIXME: don't hardcode
 	logrus.WithFields(logrus.Fields{
 		"ue-ip":         ue_ip,
 		"gnb-ip":        infos.Gnb,
@@ -234,7 +234,8 @@ func (pusher *RulesPusher) pushRTRRule(ctx context.Context, ue_ip string) error
 			return err
 		}
 		action := n4tosrv6.Action{
-			SRH: *srh,
+			SRH:        *srh,
+			SourceGtp4: r.SrgwGtp4,
 		}
 		rule := n4tosrv6.Rule{
 			Enabled: true,
diff --git a/internal/config/rule.go b/internal/config/rule.go
index 7f22db8..345194a 100644
--- a/internal/config/rule.go
+++ b/internal/config/rule.go
@@ -15,5 +15,6 @@ type Rule struct {
 	ControlURI   jsonapi.ControlURI `yaml:"control-uri"`    // e.g. http://srgw.local:8080
 	Area         *[]netip.Prefix    `yaml:"area,omitempty"` // list of gnbs in this area (can be aggregated in prefixes)
 	Enabled      bool               `yaml:"enabled"`
-	SegmentsList []string           `yaml:"segments-list"` // Segment[0] is the ultimate node, Segment[n-1] is the next hop ; Segment[0] can be a prefix (for downlink)
+	SegmentsList []string           `yaml:"segments-list"`       // Segment[0] is the ultimate node, Segment[n-1] is the next hop ; Segment[0] can be a prefix (for downlink)
+	SrgwGtp4     *netip.Addr        `yaml:"srgw-gtp4,omitempty"` // GTP4 Address of the SRGW (for downlink rules only)
 }